Database Programmingin
SQL/ORACLE
Wolfgang May
2001
Database Programming in SQL/ORACLE
SQL-3 Standard/ORACLE 8:
• ER-Modeling
• Schema Generation
• Queries
• Views
• Complex attributes, nested tables
• Database Optimization
• Access Control/Authorization
• Transactions
• Updates, Schema Modifications
• Referential Integrity
• PL/SQL: Triggers, Procedures, Functions
• Object-relational Features
• Embedded SQL
• JDBC (Embedding into Java)
Introduction 1
Database Programming in SQL/ORACLE
The Database: M ONDIAL
• Continents• Countries• Administrative
Divisions• Cities• Organizations
• Mountains• Rivers• Lakes• Seas• Deserts
• Economy• Population• Languages• Religions• Ethnic Groups
• CIA World Factbook
• “Global Statistics”: Countries, Adm. Divisions, Cities
• TERRA-Database of the Institut für Programmstrukturenund Datenorganisation der Universit"at Karlsruhe
• . . . some more Web-Pages
• Data Integration has been done with FLORIDIntroduction 2
Database Programming in SQL/ORACLE
Literature
• Textbooks on Databases (in german):
A. Kemper, A. Eickler: Datenbanksysteme - EineEinf"uhrung, Oldenbourg, 1996
G. Vossen: Datenmodelle, Datenbanksprachen undDatenbankmanagement-Systeme. Addison-Wesley, 1994.
• Textbook on SQL (in german):G. Matthiessen and M. Unterstein: RelationaleDatenbanken und SQL: Konzepte der Entwicklung undAnwendung. Addison-Wesley, 1997.
• The book on the practical DB training at Uni Karlsruhe withTERRA:M. Dürr and K. Radermacher: Einsatz vonDatenbanksystemen. Springer Verlag, 1990.
• Explanation of the SQL-2 Standard:C. Date and H. Darwen: A guide to the SQL standard: auser’s guide to the standard relational language SQL.Addison-Wesley, 1994.
• Textbooks on relational databases and SQL:
H. F. Korth and A. Silberschatz: Database SystemConcepts. McGraw-Hill, 1991.
J. Ullman and J. Widom: A First Course in DatabaseSystems. Prentice Hall, 1997.
and some more ...Introduction 3
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hip
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Con
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ntry
Pro
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Org
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Lang
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Rel
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Database Programming in SQL/ORACLE
Entities and Relationships
Province City
Country Continent
in_Prov
is_capital
belongs to is_capital
encompasses
borders
ER-Model 5
Database Programming in SQL/ORACLE
Entities
Entity type: An entity type represents a concept in the realworld. It is given as a pair (E, {A1, . . . , An}), where E isthe name and {A1, . . . , An}, n ≥ 0 are the attributes (valueproperties) of a type.
Attribute: a relevant property of entities of a given type. Eachattribute can have values from a given domain.
Entity: each entity describes a real-world object. Thus, it mustbe of one of the defined entity types E. It assigns a valueto each attribute that is declared for the entity type E.
Key attributes: a key is a set of attributes of an entity type,whose values together allow for a unique identification of allamongst all entities of a given type (cf. candidate keys,primary keys).
ER-Model 6
Database Programming in SQL/ORACLE
Entities:
Country
ent.0815
name
Germany
code
Darea
356910
population
83536115
government
federal republic
gross product
1.452.200.000 independence
1871
inflation
2%
Mountain
ent.4711
name
Feldberg
mountains
Black Forest
height
1493.8
geo coord
longitude
7.5
latitude
47.5
ER-Model 7
Database Programming in SQL/ORACLE
Relationships
Relationship type: describes a concept of relationshipsbetween entities. It is given as a triple(B, {RO1 : E1, . . . , ROk : Ek}, {A1, . . . , An}), where B isthe name, {RO1, . . . , ROk}, k ≥ 2, is a list of roles,{E1, . . . , Ek} is a list of entity types associated to the roles,and {A1, . . . , An}, n ≥ 0 is the set of attributes of therelationship type.
Roles are pairwise different – the associated entity types arenot necessarily pairwise distinct. In case that Ei = Ej fori 6= j, there is a recursive relationship.
Attribute: relevant properties of relationships of a given type.
Relationship: A relationship of a relationship type B is definedby the entities that are involved in the relationship,according to their associated roles. For each role, there isexactly one entity involved in the relationship, and everyattribute is assigned a value.
ER-Model 8
Database Programming in SQL/ORACLE
Relationships
City Countryin
Freiburg Germany
relationship with attributes
continent Countryencompasses
percentEurope Russia
20relationship with roles
City Countryis_capitalis of
Berlin Germany
recursive relationship
River flows_into
main river
tributary riverRhein, Main
ER-Model 9
Database Programming in SQL/ORACLE
Complexities of relationships
Every relationship type is assigned a complexity that specifiesthe minimal and maximal number of relationships in which anentity of a given type may be involved.
The complexity degree of a relationship type B wrt. one of itsroles RO is an expression of the form (min, max).
A set b of relationships satisfies the complexity degree(min, max) of a role RO if for all entities e of the correspondingentity type, the following holds: there exist at least min and atmost max relationships b in which e is involved in the role RO.
ER-Model 10
Database Programming in SQL/ORACLE
Relationships
Province City
Country Continent
in_Prov< 0, ∗ > < 1, ∗ >
is_capital
< 1, 1 >< 0, ∗ >
belongs to
< 1, 1 >
< 1, ∗ >
is_capital
< 1, 1 >
< 0, 1 >
encompasses< 1, ∗ > < 1, ∗ >
borders
< 0, ∗ >< 0, ∗ >
ER-Model 11
Database Programming in SQL/ORACLE
Weak Entity Types
A weak entity type is an entity type without a key.
Thus their entities must be identified by the help of anotherentity.
• Weak entity types must be involved in at least onen : 1-relationship with a strong entity type (where the strongentity type stands on the 1-side).
• They must have a local key, i.e., a set of attributes that canbe extended by the primary keys of the correspondingstrong entity type to provide a key for the weak entity type.
ER-Model 12
Database Programming in SQL/ORACLE
Weak Entity Types
Country
in
< 0, ∗ >
name
area pop.
code
248678 61170500
BRD ent_4711 D
Province
in Prov.
< 0, ∗ >
name
area pop.
35751 10272069
Baden-W.ent_1997
Cityname pop.
longitude latitude
198496
7.8 48
Freiburg ent_0815
There is also a Freiburg/CH
< 1, 1 >
and Freiburg/Elbe, LowerSaxonia (Niedersachsen)
< 1, 1 >
ER-Model 13
Database Programming in SQL/ORACLE
n-ary Relationships:
A river flows into a sea/lake/river; more detailed, this point canbe described by giving one or two countries.
river seaflows into< 0, n > < 0, n >
Country
< 0, n >
Aggregation:
Useful to introduce an Aggregate type mouth:
Mouth
river seaflows into< 0, 1 > < 0, n >
Country
in
< 1, 2 >
< 0, ∗ >
ER-Model 14
Database Programming in SQL/ORACLE
Generalization/Specialization
• Generalization: rivers, lakes, and seas are waters. Thesecan e.g. be involved in located-at relationships with cities:
Water City
g
River Lake Sea
located< 0, ∗ > < 0, ∗ >name
length depth area depth area
ER-Model 15
Database Programming in SQL/ORACLE
Generalization/Specialization
• Specialization: MONDIAL does not describe allgeographical things, but only rivers, lakes, seas,mountains, deserts, and islands (no lowlands, highlands,savannas, fens, etc). All such geographical things have incommon that they are involved in in-relationships withadministrative divisions:
Geo Province
s
River Lake Sea Mountain Island Desert
in< 1, ∗ > < 0, ∗ >name
ER-Model 16
Database Programming in SQL/ORACLE
The Relational Model
• only a single structural concept Relation for entity typesand relationship types,
• Relational Model by Codd (1970): mathematicalfoundation: set theory
• a relation schema consists of a name and a set ofattributes,Continent: Name, Area
• each attribute is associated with a Domain which specifiesthe possible values of the attribute. Often, attributes alsocan have a null value.Continent: Name: VARCHAR(25), Area: NUMBER
• elements of a relation are called tuples.(Asia,4.5E7)
A (relational) database schema R is given by a (finite) set of(relation) schemata.Continent: . . . ; Country: . . . ; City: . . .
A (database) state associates each relation schema to arelation .
The Relational Model 17
Database Programming in SQL/ORACLE
Mapping ERM to RM
Let EER an entity type and BER a relationship type in the ERM.
1. Entity types: (EER, {A1, . . . , An}) −→ E(A1, . . . , An),
2. Relationship types:(BER, {RO1 : E1, . . . , ROk : Ek}, {A1, . . . , Am}) −→
B(E1_K11, . . . , E1_K1p1, . . . ,
Ek_Kk1, . . . , Ek_Kkpk, A1, . . . , Am) ,
where {Ki1, . . . , Kipi} are the primary keys of Ei, 1 ≤ i ≤ k.
In case that for a relationship type BER, the keys ofinvolved entity types have coinciding names, the rolespecifications may be used to guarantee the uniqueness ofkey attributes in the relationship type.
In case that k = 2 and a (1,1) relationship complexity, therelation schema of the relationship type and that of theentity type may be merged.
3. For a weak entity type, the key attributes of the identifyingentity type must be added.
4. Aggregate types can be ignored if the underlyingrelationship type is mapped.
The Relational Model 18
Database Programming in SQL/ORACLE
Entity types
(EER, {A1, . . . , An}) −→ E(A1, . . . , An)
continentname area
Asia ent_79110 4.5E7
Continent
Name Area
VARCHAR(20) NUMBER
Europe 9562489.6
Africa 3.02547e+07
Asia 4.50953e+07
America 3.9872e+07
Australia 8503474.56
The Relational Model 19
Database Programming in SQL/ORACLE
Relationship Types
(BER, {RO1 : E1, . . . , ROk : Ek}, {A1, . . . , Am}) −→
B(E1_K11, . . . , E1_K1p1, . . . ,
Ek_Kk1, . . . , Ek_Kkpk, A1, . . . , Am),
where {Ki1, . . . , Kipi} are the primary keys of Ei, 1 ≤ i ≤ k. (it
is allowed to rename, e.g., to use Country for Country.Code)
continent Countryencompasses
name
Europe
code
R
percent
20
encompasses
Country Continent Percent
VARCHAR(4) VARCHAR(20) NUMBER
R Europe 20
R Asia 80
D Europe 100
. . . . . . . . .
The Relational Model 20
Database Programming in SQL/ORACLE
Relationship Types
In case that k = 2 and a (1,1) relationship complexity, therelation schema of the relationship type and that of the entitytype may be merged.
Country
City
is_capital
< 1, 1 >
< 0, 1 >
name
Germany
code
D
name
Berlin
pop.
3472009ent_0815
Country
Name code Population Capital Province ...
Germany D 83536115 Berlin Berlin
Sweden S 8900954 Stockholm Stockholm
Canada CDN 28820671 Ottawa Quebec
Poland PL 38642565 Warsaw Warszwaskie
Bolivia BOL 7165257 La Paz Bolivia
.. .. .. .. ..
The Relational Model 21
Database Programming in SQL/ORACLE
Weak Entity Types
For a weak entity type, the key attributes of the identifying entity typemust be added.
Country
in
name
area pop.
code
248678 61170500
BRD ent_4711 D
Province
in Prov.
name
area pop.
35751 10272069
Baden-W.ent_1997
Cityname pop.
198496Freiburg ent_0815
< 1, 1 >
< 1, 1 >
City
Name Country Province Population ...
Freiburg D Baden-W. 198496 ..
Berlin D Berlin 3472009 ..
.. .. .. .. ..
The Relational Model 22
Database Programming in SQL/ORACLE
Relationship Types
In case that for a relationship type B, the keys of involved entitytypes have coinciding names, the role specifications may beused to guarantee the uniqueness of key attributes in therelationship type.
Countrycode name
borders
< 0, ∗ >
C1
< 0, ∗ >
C2
borders
Country1 Country2
D F
D CH
CH F
.. ..
The Relational Model 23
Database Programming in SQL/ORACLE
SQL = Structured Query Language
• common query language
• standardization: SQL-89, SQL-2 (1992), SQL-3 (1996)
• SQL-2 in 3 stages: entry, intermediate, and full level
• SQL-3: object-orientation
• descriptive querying language
• results are always sets of tuples (relations)
• implementation: ORACLE (and many others)
• SQL is case-insensitive, i.e., CITY=city=City=cItY.
• inside quotes, SQL is not case-insensitive, i.e., City=’Berlin’6= City=’berlin’.
• every command has to be ended with a semicolon “;”
• comment lines are embraced in /∗ . . . ∗/, or introduced by-- or rem.
SQL-2 24
Database Programming in SQL/ORACLE
Data Dictionary: Contains meta data about the database
Database Language:
DDL: Data Definition Language for defining schema
• tables• views• indexes• integrity constraints
DML: Data Manipulation Language for manipulatingdatabase states
• Search/Read• Insert• Modify• Delete
SQL-2 25
Database Programming in SQL/ORACLE
Data Dictionary
Consists of tables and views that contain meta data about thedatabase.
With SELECT * FROM DICTIONARY (abbrev. SELECT * FROM
DICT),the Data Dictionary explains itself.
TABLE_NAME
COMMENTS
ALL_ARGUMENTS
Arguments in objects accessible to the user
ALL_CATALOG
All tables, views, synonyms, sequences accessible to the user
ALL_CLUSTERS
Description of clusters accessible to the user
ALL_CLUSTER_HASH_EXPRESSIONS
Hash functions for all accessible clusters...
Data Dictionary 26
Database Programming in SQL/ORACLE
Data Dictionary
ALL_OBJECTS: contains all objects that are accessible for auser.
ALL_CATALOG: contains all tables, views, and synonyms thatare accessible for a user.
ALL_TABLES: contains all tables that are accessible for a user.
Analogously for several other things. (select * from
ALL_CATALOG where TABLE_NAME LIKE ’ALL%’;).
USER_OBJECTS: contains all objects that where the user is theowner.
Analogously for other database object types, in most casethere is also an abbreviation for USER_..., e.g. OBJ forUSER_OBJECTS.
ALL_USERS: contains informations about all users of thedatabase.
Data Dictionary 27
Database Programming in SQL/ORACLE
SELECT table_name FROM tabs;
Table_name
BORDERS
CITY
CONTINENT
COUNTRY
DESERT
ECONOMY
ENCOMPASSES
ETHNIC_GROUP
GEO_DESERT
GEO_ISLAND
GEO_LAKE
GEO_MOUNTAIN
GEO_RIVER
GEO_SEA
Table_name
ISLAND
LAKE
LANGUAGE
LOCATED
IS_MEMBER
MERGES_WITH
MOUNTAIN
ORGANIZATION
POLITICS
POPULATION
PROVINCE
RELIGION
RIVER
SEA
28 rows selected.
Data Dictionary 28
Database Programming in SQL/ORACLE
The schema of individual tables and views can be displayed byusing DESCRIBE <table> or abbreviated DESC <table>:
DESC City;
Name NULL? Typ
NAME NOT NULL VARCHAR2(25)
COUNTRY NOT NULL VARCHAR2(4)
PROVINCE NOT NULL VARCHAR2(35)
POPULATION NUMBER
LONGITUDE NUMBER
LATITUDE NUMBER
Data Dictionary 29
Database Programming in SQL/ORACLE
Queries: SELECT-FROM-WHERE
Queries against the database are in SQL formulated by theSELECT command. Its basic structure is simple:
SELECT Attributes
FROM Relation(s)
WHERE Condition
Simplest form: all columns and rows of a relation
SELECT * FROM City;
Name C. Province Pop. Long. Lat.
......
......
......
Vienna A Vienna 1583000 16,3667 48,25
Innsbruck A Tyrol 118000 11,22 47,17
Stuttgart D Baden-W. 588482 9.1 48.7
Freiburg D Germany 198496 NULL NULL...
......
......
...
3114 rows selected.
SQL: Queries 30
Database Programming in SQL/ORACLE
Projection: Choose some columns
SELECT <attr-list>
FROM <table>;
For all cities, give its name and the country to which it belongs:
SELECT Name, Country
FROM City;
Name COUNTRY
Tokyo J
Stockholm S
Warsaw PL
Cochabamba BOL
Hamburg D
Berlin D
.. ..
SQL: Queries 31
Database Programming in SQL/ORACLE
DISTINCT
SELECT * FROM Island;
Name Islands Area ...
......
......
Jersey Channel Islands NULL . . .
Mull Inner Hebrides 910 . . .
Montserrat Antilles 106 . . .
Grenada Antilles NULL . . ....
......
...
SELECT Islands
FROM Island;
Islands...
Channel Islands
Inner Hebrides
Antilles
Antilles...
SELECT DISTINCT Islands
FROM Island;
Islands...
Channel Islands
Inner Hebrides
Antilles...
SQL: Queries 32
Database Programming in SQL/ORACLE
Duplicate Elimination
• Duplicates are not automatically eliminated:
– duplicate elimination is expensive (sorting and deleting)
– user may be interested in duplicates
– later: aggregate functions on relations with duplicates
• Duplicate elimination: DISTINCT-clause
• later: Duplicates are automatically eliminated when setoperations UNION, INTERSECT, ... are used
SQL: Queries 33
Database Programming in SQL/ORACLE
Selections: Choose some rows
SELECT <attr-list>
FROM <table>
WHERE <predicate>;
<predicate> may be of the following forms:
• <attribute> <op> <value> with op ∈ {=, <, >, <=, >=},
• <attribute> [NOT] LIKE <string>, where each underscorein the string stands for an arbitrary character, and “%”stands for arbitrary many characters,
• <attribute> IN <value-list>, where <value-list> is either ofthe form (’val1’,. . . ,’valn’), or may be given as the result of asubquery,
• [NOT] EXISTS <subquery>
• NOT (<predicate>),
• <predicate> AND <predicate>,
• <predicate> OR <predicate>.
SQL: Queries 34
Database Programming in SQL/ORACLE
Example:
SELECT Name, Country, Population
FROM City
WHERE Country = ’J’;
Name Country Population
Tokyo J 7843000
Kyoto J 1415000
Hiroshima J 1099000
Yokohama J 3256000
Sapporo J 1748000...
......
Example:
SELECT Name, Country, Population
FROM City
WHERE Country = ’J’ AND Population > 2000000
Name Country Population
Tokyo J 7843000
Yokohama J 3256000
SQL: Queries 35
Database Programming in SQL/ORACLE
Example:
SELECT Name, Country, Population
FROM City
WHERE Country LIKE ’%J_%’;
Name Country Population
Kingston JA 101000
Amman JOR 777500
Suva FJI 69481...
......
The requirement that the “J” is followed by at least onecharacter excludes japanese cities (“J”) from the result.
SQL: Queries 36
Database Programming in SQL/ORACLE
ORDER BY
SELECT Name, Country, Population
FROM City
WHERE Population > 5000000
ORDER BY Population DESC; (descending)
Name Country Population
Seoul ROK 10.229262
Mumbai IND 9.925891
Karachi PK 9.863000
Mexico MEX 9.815795
Sao Paulo BR 9.811776
Moscow R 8.717000...
......
SQL: Queries 37
Database Programming in SQL/ORACLE
ORDER BY, Alias
SELECT Name, Population/Area AS Density
FROM Country
ORDER BY 2 ; (Default: ascending)
Name Density
Western Sahara ,836958647
Mongolia 1,59528243
French Guiana 1,6613956
Namibia 2,03199228
Mauritania 2,26646745
Australia 2,37559768
SQL: Queries 38
Database Programming in SQL/ORACLE
Aggregate functions
• COUNT (*| [DISTINCT] <attribute>)
• MAX (<attribute>)
• MIN (<attribute>)
• SUM ([DISTINCT] <attribute>)
• AVG ([DISTINCT] <attribute>)
Example: How many cities are stored in the database?
SELECT Count (*)
FROM City;
Count(*)
3114
Example: How many countries are stored in the database forwhich at least one city with more than 1,000,000 inhabitants isstored?
SELECT Count (DISTINCT Country)
FROM City
WHERE Population > 1000000;
Count(DISTINCT(Country))
68
Aggregate functions 39
Database Programming in SQL/ORACLE
Aggregate functions
Example: Compute the sum of the population of all Austriancities, and the number of inhabitants of Austria’s largest city.
SELECT SUM(Population), MAX(Population)
FROM City
WHERE Country = ’A’;
SUM(Population) MAX(Population)
2434525 1583000
And what, if these values are needed for each of thecountries??
Aggregate functions 40
Database Programming in SQL/ORACLE
Grouping
GROUP BY conputes one row for every group. This groupcontains data that is obtained by using aggregate functionsover all rows of the group.
SELECT <expr-list>
FROM <table>
WHERE <predicate>
GROUP BY <attr-list>;
returns for every value of <attr-list> a single row. Thus, in<expr-list> only the following expressions are allowed:
• constants,
• attribute from <attr-list>,
• attribute, which have the same value for all rows in such agroup (e.g. Code, if <attr-list> contains Country),
• Aggregate functions, which are then applied to all tuples ofthe corresponding group.
The WHERE clause <predicate> contains only attributes of therelations mentioned in <table> (i.e., no aggregate functions).
Grouping 41
Database Programming in SQL/ORACLE
Grouping
Example: For every country, return the number of inhabitantsthat live in cities.
SELECT Country, Sum(Population)
FROM City
GROUP BY Country;
Country SUM(Population)
A 2434525
AFG 892000
AG 36000
AL 475000
AND 15600...
...
Grouping 42
Database Programming in SQL/ORACLE
Conditions over Groups
The HAVING clause allows to state additional conditions on thegroups:
SELECT <expr-list>
FROM <table>
WHERE <predicate1>
GROUP BY <attr-list>
HAVING <predicate2>;
• WHERE clause: conditions on individual tuples beforegrouping,
• HAVING clause: conditions to select groups for the result. Inthe HAVING clause, in addition to aggregate functionexpressions over attributes, only those attributes areallowed that are mentioned explicitly in the GROUP BY
clause.
Grouping 43
Database Programming in SQL/ORACLE
Conditions on Groups
Example: Compute for each country the total number ofinhabitants that live in cities with more than 100,000inhabitants. Output only those countries where this number ismore than 10 millions.
SELECT Country, SUM(Population)
FROM City
WHERE Population > 10000
GROUP BY Country
HAVING SUM(Population) > 10000000;
Country SUM(Population)
AUS 12153500
BR 77092190
CDN 10791230
CO 18153631...
...
Grouping 44
Database Programming in SQL/ORACLE
Set Operations
SQL queries can be joined by set operations:
<select-clause> <set-op> <select-clause>;
• UNION [ALL]
• MINUS [ALL]
• INTERSECT [ALL]
• automatical elemination of duplicates (can be prevented byALL)
Example: Give all names of cities that also occur as names ofcountries:
(SELECT Name
FROM City)
INTERSECT
(SELECT Name
FROM Country);
Name
Armenia
Djibouti
Guatemala...
Set Operations 45
Database Programming in SQL/ORACLE
Join Queries
Join queries provide a possibility to combine several relationsinto a query.
SELECT <attr-list>
FROM <table-list>
WHERE <predicate>;
Basically, a join is based on the cartesian product of thecontributing relations (Theory: see “Introduction toDatabases”).
• resulting attributes: union of all attributes of contributingrelations
• attributes that occur in several relations must be qualifiedby <table>.<attr>.
• join of a relation with itself – aliases.
Join Queries 46
Database Programming in SQL/ORACLE
Example: All countries that have less inhabitants than Tokyo.
SELECT Country.Name, Country.Population
FROM City, Country
WHERE City.Name = ’Tokyo’
AND Country.Population < City.Population;
Name Einwohner
Albania 3249136
Andorra 72766
Liechtenstein 31122
Slovakia 5374362
Slovenia 1951443...
...
Join Queries 47
Database Programming in SQL/ORACLE
Equijoin
Example: For all organizations, give the continents where theyare seated.
encompasses: Country, Continent, Percentage.
Organization: Abbreviation, Name, City, Country, Province.
SELECT Continent, Abbreviation
FROM encompasses, Organization
WHERE encompasses.Country = Organization.Country;
Name Organization
America UN
Europe UNESCO
Europe CCC
Europe EU
America CACM
Australia/Oceania ANZUS...
...
Join Queries 48
Database Programming in SQL/ORACLE
Join of a relation with itself
Example: Compute all pairs of cities in different countrieswhich have the same name.
SELECT A.Name, A.Country, B.Country
FROM City A, City B
WHERE A.Name = B.Name
AND A.Country < B.Country;
A.Name A.Country B.Country
Alexandria ET RO
Alexandria ET USA
Alexandria RO USA
Barcelona E YV
Valencia E YV
Salamanca E MEX...
......
Join Queries 49
Database Programming in SQL/ORACLE
Subqueries
The WHERE clause can contain results of subqueries:
SELECT <attr-list>
FROM <table>
WHERE <attribute> (<op> [ANY|ALL]| IN) <subquery>;
• <subquery> is a SELECT query (Subquery),
• for <op> ∈ {=, <, >, <=, >=}, <subquery> must result in arelation with a single column,
• for IN <subquery>, also multi-column results are allowed(since ORACLE 8),
• for <op> without ANY or ALL, the result of <subquery> mustcontain only a single row.
Subqueries 50
Database Programming in SQL/ORACLE
Uncorrelated Subquery
• independent from the values of the tuple which is currentlyprocessed in the surrounding query,
• evaluated once before the surrounding query,
• the result is then used for evaluating the WHERE clause ofthe surrounding query,
• strictly sequential evaluation, thus, the qualification ofmultiply occurring attributes is not necessary.
Example: Give all countries where there exists a city withname “Victoria”:
SELECT Name
FROM Country
WHERE Code IN
(SELECT Country
FROM City
WHERE Name = ’Victoria’);
Country.Name
Canada
SeychellesSubqueries 51
Database Programming in SQL/ORACLE
Uncorrelated Subquery with IN
Example: Give all cities that are known to be situated at ariver, lake, or a sea:
SELECT *
FROM CITY
WHERE (Name,Country,Province)
IN (SELECT City,Country,Province
FROM located);
Name Country Province Population ...
Ajaccio F Corse 53500 . . .
Karlstad S Värmland 74669 . . .
San Diego USA California 1171121 . . ....
......
Subqueries 52
Database Programming in SQL/ORACLE
Subquery with ALL
Example: ALL can e.g. be used for computing all countries thatare smaller than all countries that have more than 10 millioninhabitants:
SELECT Name,Area,Population
FROM Country
WHERE Area < ALL
(SELECT Area
FROM Country
WHERE Population > 10000000);
Name Area Population
Albania 28750 3249136
Macedonia 25333 2104035
Andorra 450 72766...
......
Subqueries 53
Database Programming in SQL/ORACLE
Correlated Subquery
• Subquery depends on attribute values of the tuple which iscurrently processed in the outer query,
• evaluated once for every tuple of the surrounding query,
• imported attributes must be qualified.
Example: Compute all cities where more than 1/4 of thepopulation of the corresponding country is living.
SELECT Name, Country
FROM City
WHERE Population * 4 >
(SELECT Population
FROM Country
WHERE Code = City.Country);
Name Country
Copenhagen DK
Tallinn EW
Vatican City V
Reykjavik IS
Auckland NZ...
...
Subqueries 54
Database Programming in SQL/ORACLE
The EXISTS Operator
EXISTS and NOT EXISTS simulate the existential quantifier.
SELECT <attr-list>
FROM <table>
WHERE [NOT] EXISTS
(<select-clause>);
Example: Compute all countries for which cities with morethan 1,000,000 inhabitants are stored.
SELECT Name
FROM Country
WHERE EXISTS
( SELECT *
FROM City
WHERE Population > 1000000
AND City.Country = Country.Code) ;
Name
Serbia and Montenegro
France
Spain
Austria...
Subqueries 55
Database Programming in SQL/ORACLE
Transformation EXISTS, Subquery, Join
Equivalent to the previous one are the following queries:
SELECT Name
FROM Country
WHERE Code IN
( SELECT Country
FROM City
WHERE City.Population > 1000000);
SELECT DISTINCT Country.Name
FROM Country, City
WHERE City.Country = Country.Code
AND City.Population > 1000000;
Subqueries 56
Database Programming in SQL/ORACLE
Example
A country is strongly urbanized if more than 10 percent of itspopulation live in cities with more than 500,000 inhabitants.Which member countries of the EU are strongly urbanized?
SELECT Country.Name
FROM Country, City, is_member
WHERE Organization = ’EU’
AND is_member.Country = Country.Code
AND is_member.Type = ’member’
AND City.Population > 500000
AND City.Country = Country.Code
GROUP BY Country.Name, Country.Population
HAVING (SUM(City.Population)/Country.Population) > 0.1;
Name
Austria
Denmark
Germany
Ireland
Italy
Netherlands
Spain
United Kingdom
Subqueries 57
Database Programming in SQL/ORACLE
Subqueries in the FROM Clause
SELECT <attr-list>
FROM <table/subquery-list>
WHERE <condition>;
Values which are obtained in different ways from differenttables can be related.
Example: Compute the total number of people who do not livein the stored cities.
SELECT Population - Urban_Residents
FROM
(SELECT SUM(Population) AS Population
FROM Country),
(SELECT SUM(Population) AS Urban_Residents
FROM City);
Population-Urban_Residents
4620065771
Subqueries 58
Database Programming in SQL/ORACLE
Subqueries in the FROM Clause
... especially suitable for nested computations with aggregatefunctions
Example: Compute the total number of people who live in thelargest city of their countries.
SELECT sum(pop_biggest)
FROM (SELECT country, max(population) as pop_biggest
FROM City
GROUP BY country);
sum(pop_biggest)
273837106
Subqueries 59
Database Programming in SQL/ORACLE
Schema Definition
• the database schema contains all information about thestructure of the database,
• tables, views, constraints, indexes, clusters, triggers ...
• ORACLE 8: datatypes, methods
• is defined and modified using the DDL (Data DefinitionLanguage),
• CREATE, ALTER, and DROP of schema objects,
• access rights: GRANT.
Schema Definition 60
Database Programming in SQL/ORACLE
Generation of Tables
CREATE TABLE <table>
(<col> <datatype>,...
<col> <datatype>)
CHAR(n): string with fixed length n.
VARCHAR2(n): string with variable length ≤ n.||: string concatenation.
NUMBER: numbers. for NUMBER, the usual operators +, −, ∗, and/, and the comparisons =, >, >=, <=, and < are allowed.Additionally there is BETWEEN x AND y.Inequality: ! =, ∧ =, ¬ =, or <>.
DATE: Dates and times: Century – Year – Month – Day – Hour– Minute – Second. There is also arithmetics and somemore functions for these datatypes.
additional Datatypes are described in the manual.
Schema Definition 61
Database Programming in SQL/ORACLE
Table Definition
The below SQL statement generates the City relation (stillwithout integrity constraints):
CREATE TABLE City
( Name VARCHAR2(35),
Country VARCHAR2(4),
Province VARCHAR2(32),
Population NUMBER,
Longitude NUMBER,
Latitude NUMBER );
Schema Definition 62
Database Programming in SQL/ORACLE
Definition of Tables: Constraints
With the definition of tables, properties and constraints on theattribute values can be specified.
• Constraints on a single or on several attributes:
• Constraints on the domain,
• Specification of default values,
• NULL values allowed or not,
• Specification of key constraints,
• Predicates over each individual tuple.
Syntax:
CREATE TABLE <table>
(<col> <datatype> [DEFAULT <value>]
[<colConstraint> ... <colConstraint>],...
<col> <datatype> [DEFAULT <value>]
[<colConstraint> ... <colConstraint>],
[<tableConstraint>,]...
[<tableConstraint>])
• <colConstraint> concerns only a single column,
• <tableConstraint> can concern several columns.Schema Definition 63
Database Programming in SQL/ORACLE
Definition of Tables: Default Values
DEFAULT <value>
A member country of an organization is assumed to be a fullmember if nothing else is specified:
CREATE TABLE is_member
( Country VARCHAR2(4),
Organization VARCHAR2(12),
Type VARCHAR2(30)
DEFAULT ’member’)
INSERT INTO is_member VALUES
(’CZ’, ’EU’, ’membership applicant’);
INSERT INTO is_member (Land, Organization)
VALUES (’D’, ’EU’);
Country Organization Type
CZ EU membership applicant
D EU member...
......
Schema Definition 64
Database Programming in SQL/ORACLE
Definition of Tables: Constraints
Two types of constraints:
• A column condition <colConstraint> is a condition that isconcerned only with a single column (to which it isassociated)
• A table condition <tableConstraint> may concern severalcolumns.
Each <colConstraint> or <tableConstraint> is of the form
[CONSTRAINT <name>] <condition>
Schema Definition 65
Database Programming in SQL/ORACLE
Definition of Tables: Conditions (Overview)
Syntax:
[CONSTRAINT <name>] <condition>
Keywords in <condition>:
1. CHECK (<condition>): no line is allowed to violate<condition>. NULL values result in an unknown that doesnot violate any check condition.
2. [NOT] NULL: indicates whether a column is allowed tocontain null values (only as <colConstraint>).
3. UNIQUE (<column-list>): requires every value in acolumn to be unique (wrt. all tuples in this table).
4. PRIMARY KEY (<column-list>): Declares the givencolumns as primary keys of this table.
5. FOREIGN KEY (<column-list>) REFERENCES
<table>(<column-list2>) [ON DELETE CASCADE|ON
DELETE SET NULL]:declares a set of attributes to be a foreign key.
Schema Definition 66
Database Programming in SQL/ORACLE
Definition of Tables: Syntax
[CONSTRAINT <name>] <condition>
where CONSTRAINT <name> is optional (otherwise, an internalname is assigned).
• <name> is needed for NULL-, UNIQUE-, CHECK-, andREFERENCES-constraints, if the constraint should bechanged or deleted eventually,
• PRIMARY KEY can be changed or deleted without having anexplicit name.
Since for a <colConstraint>, the column is implicitly known,the (<column-list>) part is omitted.
Schema Definition 67
Database Programming in SQL/ORACLE
Definition of Tables: CHECK Constraints
• as column constraints: domain constraint
CREATE TABLE City
( Name VARCHAR2(35),
Population NUMBER CONSTRAINT CityPop
CHECK (Population >= 0),
...);
• as table constraints: arbitrary integrity constraints on thevalues of each individual tuple.
Schema Definition 68
Database Programming in SQL/ORACLE
Definition of Tables: PRIMARY KEY, UNIQUE, andNULL
• PRIMARY KEY (<column-list>): declares these columnsto be the primary key of a table.
• PRIMARY KEY is equivalent to combining UNIQUE and NOT
NULL.
• UNIQUE is not necessarily violated by NULL values, whereasPRIMARY KEY forbids NULL values.
One Two
a b
a NULL
NULL b
NULL NULL
satisfies UNIQUE (One,Two).
• Since for each table, only one PRIMARY KEY may bedefined, candidate keys must be specified by NOT NULL andUNIQUE.
Relation Country : Code is the PRIMARY KEY, Name is acandidate key:
CREATE TABLE Country
( Name VARCHAR2(32) NOT NULL UNIQUE,
Code VARCHAR2(4) PRIMARY KEY);
Schema Definition 69
Database Programming in SQL/ORACLE
Definition of Tables: FOREIGN KEY ...REFERENCES
• FOREIGN KEY (<column-list>) REFERENCES
<table>(<column-list2>) [ON DELETE CASCADE|ON
DELETE SET NULL]: declares the attribute tuple<column-list> of the table to be a foreign key thatreferences the attribute tuple <column-list2> of the table<table>.
• The referenced attribute tuple <table>(<column-list2>)
must be declared as PRIMARY KEY of <table>.
• A REFERENCES condition is not violated by NULL values.
• ON DELETE CASCADE|ON DELETE SET NULL: referentialaction (later).
CREATE TABLE is_member
(Country VARCHAR2(4)
REFERENCES Country(Code),
Organization VARCHAR2(12)
REFERENCES Organization(Abbreviation),
Type VARCHAR2(30) DEFAULT ’member’);
Schema Definition 70
Database Programming in SQL/ORACLE
Definition of Tables: Foreign Keys
A mountain is located in a province of come country:
Country
Mountain Province
belongs_to
in
Name
Code
Name
CREATE TABLE geo_Mountain
( Mountain VARCHAR2(20)
REFERENCES Mountain(Name),
Country VARCHAR2(4) ,
Province VARCHAR2(32) ,
CONSTRAINT GMountRefsProv
FOREIGN KEY (Country,Province)
REFERENCES Province (Country,Name));
Schema Definition 71
Database Programming in SQL/ORACLE
Definition of Tables
Complete definition of the table City, including conditions andkeys:
CREATE TABLE City
( Name VARCHAR2(35),
Country VARCHAR2(4)
REFERENCES Country(Code),
Province VARCHAR2(32) – + <tableConstraint>
Population NUMBER CONSTRAINT CityPop
CHECK (Population >= 0),
Longitude NUMBER CONSTRAINT CityLong
CHECK ((Longitude >= -180) AND (Longitude <= 180)),
Latitude NUMBER CONSTRAINT CityLat
CHECK ((Latitude >= -90) AND (Latitude <= 90)),
CONSTRAINT CityKey
PRIMARY KEY (Name, Country, Province),
FOREIGN KEY (Country,Province)
REFERENCES Province (Country,Name));
• if a table is generated with a REFERENCES
<table>(<column-list>) clause, <table> must alreadybe defined, and <column-list> must be declared asPRIMARY KEY.
Schema Definition 72
Database Programming in SQL/ORACLE
Views
• Virtual tables
• are not computed at the time of their definition, but are
• computed each time when they are accessed.
• mirror the current state of the database.
• modifications (of the data) are restricted.
CREATE [OR REPLACE] VIEW <name> (<column-list>) AS
<select-clause>;
Example: A user ofte needs the information in which countrysome city is located, but is not interested in country codes andpopulation:
CREATE VIEW CityCountry (City, Country) AS
SELECT City.Name, Country.Name
FROM City, Country
WHERE City.Country = Country.Code;
If a user now searches for all cities in Cameroon, he can statethe following query:
SELECT *
FROM CityCountry
WHERE Country = ’Cameroon’;
Views 73
Database Programming in SQL/ORACLE
Deleting Tables and Views
• tables and views are deleted with DROP TABLE or DROPVIEW:
DROP TABLE <table-name> [CASCADE CONSTRAINTS];
DROP VIEW <view-name>;
• tables need not to be empty when they are deleted.
• it is not possible to delete a table that contains referencedtuples.
• a table which is still a target of a REFERENCES declarationcannot be deleted by a simple DROP TABLE command.
• with DROP TABLE <table> CASCADE CONSTRAINTS a tableis deleted together with all referential integrity constraintsthat point to it.
Modification of Tables and Views
later.
Deleting Tables and Views 74
Database Programming in SQL/ORACLE
Inserting Information
• INSERT statement.
• insert individual tuples manually,
INSERT INTO <table>[(<column-list>)]
VALUES (<value-list>);
or
• insert the result of a query:
INSERT INTO <table>[(<column-list>)]
<subquery>;
• remaining columns are filled with null values.
E.g., insert the subsequent tuple:
INSERT INTO Country (Name, Code, Population)
VALUES (’Lummerland’, ’LU’, 4);
A table Metropolis (Name, Country, Population) can bepopulated by the following statement:
INSERT INTO Metropolis
SELECT Name, Country, Population
FROM City
WHERE Population > 1000000;
Inserting Information 75
Database Programming in SQL/ORACLE
Deletion of Tuples
Tuples can be deleted with the DELETE command:
DELETE FROM <table>
WHERE <predicate>;
With an empty WHERE clause, all tuples of a table are deleted(the table itself remains, it can be removed with DROP TABLE):
DELETE FROM City;
The below command deletes all cities that have less than50,000 inhabitants:
DELETE FROM City
WHERE Population < 50000;
Inserting Information 76
Database Programming in SQL/ORACLE
Modifying Tuples
UPDATE <table>
SET <attribute> = <value> | (<subquery>),...
<attribute> = <value> | (<subquery>),
(<attribute-list>) = (<subquery>),...
(<attribute-list>) = (<subquery>)
WHERE <predicate>;
Example:
UPDATE City
SET Name = ’Leningrad’,
Population = Population + 1000,
WHERE Name = ’Sankt-Peterburg’;
Beispiel: Set the total population of each country to the sum ofthe population of its administrative divisions:
UPDATE Country
SET Population = (SELECT SUM(Population)
FROM Province
WHERE Province.Country=Country.Code);
Modifying Tuples 77
Database Programming in SQL/ORACLE
Date and Time
The DATE datatype stores century, year, month, day, hour,minute, second.
• Set input format by NLS_DATE_FORMAT,
• Default: ’DD-MON-YY’ e.g., ’20-Oct-97’.
CREATE TABLE Politics
( Country VARCHAR2(4),
Independence DATE,
Government VARCHAR2(120));
ALTER SESSION SET NLS_DATE_FORMAT = ’DD MM YYYY’;
INSERT INTO politics VALUES
(’B’,’04 10 1830’,’constitutional monarchy’);
All countries that have been founded between 1200 and 1600:
SELECT Country, Independence
FROM Politics
WHERE Independence BETWEEN
’01 01 1200’ AND ’31 12 1599’;
Land Datum
MC 01 01 1419
NL 01 01 1579
E 01 01 1492
THA 01 01 1238
Date and Time 78
Database Programming in SQL/ORACLE
Date and Time
ORACLE provides some functions for working with DATE
information:
• SYSDATE returns the current date/time.
• addition und subtraction of absolute values over DATE isallowed. Numbers are interpreted as days: SYSDATE + 1 istomorrow, SYSDATE + (10/1440) is “in ten minutes”.
• ADD_MONTHS(d, n) adds n months to a date d.
• LAST_DAY(d) yields the last day of a the month to which d
belongs.
• MONTHS_BETWEEN(d1,d2) returns the number of monthsbetween two dates.
Date and Time 79
Database Programming in SQL/ORACLE
Object Orientation in O RACLE 8
• complex data types:
Mountain
name
height
geo coord
longitude
latitude
• nested tables:
Nested_Languages
Country Languages
D German 100
CH German 65
French 18
Italian 12
Romansch 1
FL NULL
F French 100...
...
• objects, methods, object tables, object references ...(later)
Complex Data Types 80
Database Programming in SQL/ORACLE
Generation of Data Types
New class of schema objects: CREATE TYPE
• CREATE [OR REPLACE] TYPE <name> AS OBJECT
(<attr> <datatype>,...
<attr> <datatype>);
For “full” objects, there is also aCREATE TYPE BODY ... where the methods are defined inPL/SQL ... later.
Without body/methods, simply complex datatypes aregenerated (similar to Records).
• CREATE [OR REPLACE] TYPE <name>
AS TABLE OF <datatype>
(“Collection”, tables as data types)
Complex Data Types 81
Database Programming in SQL/ORACLE
Complex Data Types
Geographical coordinates:
CREATE TYPE GeoCoord AS OBJECT
( Longitude NUMBER,
Latitude NUMBER);
/
CREATE TABLE Mountain
( Name VARCHAR2(20),
Height NUMBER,
Coordinates GeoCoord);
CREATE TYPE <type> AS OBJECT (...) automatically definesa Constructor method <type>:
INSERT INTO Mountain
VALUES (’Feldberg’, 1493, GeoCoord(8,48));
SELECT * FROM Mountain;
Name Height Coordinates(Longitude, Latitude)
Feldberg 1493 GeoCoord(8,48)
Complex Data Types 82
Database Programming in SQL/ORACLE
Complex Data Types
Access to individual components of complex attributes uses thecommon dot-Notation (similar to records).ORACLE 8.0: only with qualification:
SELECT Name, B.Coordinates.Longitude,
B.Coordinates.Latitude
FROM Mountain B;
Name Coordinates.Longitude Coordinates.Latitude
Feldberg 8 48
Complex Data Types 83
Database Programming in SQL/ORACLE
Nested Tables
CREATE [OR REPLACE] TYPE <inner_type>
AS OBJECT (...);
/
CREATE [OR REPLACE] TYPE <inner_table_type> AS
TABLE OF <inner_type>;
/
CREATE TABLE <table_name>
(... ,
<table-attr> <inner_table_type> ,
... )
NESTED TABLE <table-attr> STORE AS <name >;
CREATE TYPE Language_T AS OBJECT
( Name VARCHAR2(50),
Percentage NUMBER );
/
CREATE TYPE Languages_list AS
TABLE OF Language_T;
/
CREATE TABLE NLanguage
( Country VARCHAR2(4),
Languages Languages_list)
NESTED TABLE Languages STORE AS Languages_nested;
Nested Tables 84
Database Programming in SQL/ORACLE
Nested Tables
CREATE TYPE Language_T AS OBJECT
( Name VARCHAR2(50),
Percentage NUMBER );
/
CREATE TYPE Languages_list AS
TABLE OF Language_T;
/
CREATE TABLE NLanguage
( Country VARCHAR2(4),
Languages Languages_list)
NESTED TABLE Languages STORE AS Languages_nested;
Again: constructor methods
INSERT INTO NLanguage
VALUES( ’SK’,
Languages_list
( Language_T(’Slovak’,95),
Language_T(’Hungarian’,5)));
Nested Tables 85
Database Programming in SQL/ORACLE
Nested Tables
SELECT *
FROM NLanguage
WHERE Country=’CH’;
Country Languages(Name, Percentage)
CH Languages_List(Language_T(’French’, 18),
Language_T(’German’, 65),
Language_T(’Italian’, 12),
Language_T(’Romansch’, 1))
SELECT Languages
FROM NLanguage
WHERE Country=’CH’;
Languages(Name, Percentage)
Languages_List(Language_T(’French’, 18),
Language_T(’German’, 65),
Language_T(’Italian’, 12),
Language_T(’Romansch’, 1))
Nested Tables 86
Database Programming in SQL/ORACLE
Querying Contents of Nested Tables
Contents of inner tables:
THE (SELECT <table-attr> FROM ...)
SELECT ...
FROM THE (<select-statement>)
WHERE ... ;
INSERT INTO THE (<select-statement>)
VALUES ... / SELECT ... ;
DELETE FROM THE (<select-statement>)
WHERE ... ;
SELECT Name, Percentage
FROM THE( SELECT Languages
FROM NLanguage
WHERE Country=’CH’);
Name Percentage
German 65
French 18
Italian 12
Romansch 1
Nested Tables 87
Database Programming in SQL/ORACLE
Copying Nested Tables
Nested tables can be inserted “as a whole” if the set of tuples isstructured (casted) as a collection:
CAST(MULTISET(SELECT ...) AS <nested-table-type>)
INSERT INTO NLanguage -- allowed, but wrong !!!!
(SELECT Country,
CAST(MULTISET(SELECT Name, Percentage
FROM Language
WHERE Country = A.Country)
AS Languages_List)
FROM Language A);
each tuple (country, languageList) n-times(n = number of languages in this country) !!
INSERT INTO NLanguage (Country)
(SELECT DISTINCT Country
FROM Language);
UPDATE NLanguage B
SET Languages =
CAST(MULTISET(SELECT Name, Percentage
FROM Language A
WHERE B.Country = A.Country)
AS Languages_List);
Nested Tables 88
Database Programming in SQL/ORACLE
Nested Tables
If a query already results in a table, this can be inserted as awhole:
INSERT INTO <table>
VALUES (..., THE ( SELECT <attr>
FROM <table’>
WHERE ...) );
INSERT INTO NLanguage VALUES
(’CHXX’, THE (SELECT Languages from NLanguage
WHERE Country=’CH’));
Nested Tables 89
Database Programming in SQL/ORACLE
Working with Nested Tables
Not too simple ... (ORACLE 8.0)
• Subquery may only return a single nested table. ⇒ notpossible to select an inner table, depending on thesurrounding tuple:
All countries where german is spoken:
SELECT Country -- NOT ALLOWED !!!!
FROM NLanguage A,
THE ( SELECT Languages
FROM NLanguage B
WHERE B.Country=A.Country)
WHERE Name=’German’);
Nested Tables 90
Database Programming in SQL/ORACLE
Working with Nested Tables
TABLE ([<table>.]<attr>)
can be used in Subquery :
SELECT Country
FROM NLanguage
WHERE EXISTS
(SELECT *
FROM TABLE (Languages) -- to the current tuple
WHERE Name=’German’);
Country
A
B
CH
D
NAM
But: Attributes of the inner table cannot be selected in the outerSELECT statement.
⇒ not possible to return the percentage of the languages in thecorresponding countries.
Nested Tables 91
Database Programming in SQL/ORACLE
Working with Nested Tables
CURSOR-Operator:
Example:
SELECT Country,
CURSOR (SELECT *
FROM TABLE (Languages))
FROM NLanguage;
Country CURSOR(SELECT...)
CH CURSOR STATEMENT : 2
NAME PERCENTAGE
French 18
German 65
Italian 12
Romansch 1
⇒ Cursors etc. in PL/SQL.
Nested Tables 92
Database Programming in SQL/ORACLE
Working with Nested Tables
SELECT Country, Name -- NOT ALLOWED !!
FROM NLanguage A,
THE ( SELECT Languages
FROM NLanguage B
WHERE B.Country=A.Country);
SELECT Country, Name
FROM NLanguage A,
THE ( SELECT Languages
FROM NLanguage B
WHERE B.Country=A.Country)
WHERE A.Country = ’CH’; -- now allowed.
Using a table All_Languages that contains all languages:
SELECT Country, Name
FROM NLanguage, All_Languages
WHERE Name IN
(SELECT Name
FROM TABLE (Languages));
Conclusion: the domain of nested tables must be accessible ina single table.
Nested Tables 93
Dat
abas
eP
rogr
amm
ing
inS
QL/
OR
AC
LE
Com
plex
Dat
aTy
pes
SELECT
*FROM
USER_TYPES
Type
_nam
eTy
pe_o
idTy
peco
deA
ttrib
utes
Met
hods
Pre
Inc
Geo
Coo
rd_
Obj
ect
20
NO
NO
Lang
uage
_T_
Obj
ect
20
NO
NO
Lang
uage
s_Li
st_
Col
lect
ion
00
NO
NO
Del
ete:
DROP
TYPE
[FORCE]
With
FORCE,a
data
type
can
bede
lete
dw
hose
defin
ition
isst
illne
eded
byot
her
type
s.
Sam
esc
enar
io:
DROP
TYPE
Language_T
“Typ
mit
abh"
angi
gen
Type
nod
erta
bles
kann
nich
tgel
"osc
htod
erer
setz
twer
den”
DROP
TYPE
Language_T
FORCE
dele
tes
Language_T,b
ut
SQL>
desc
Languages_List;
FEHLER:
ORA-24372:
Ung"ultiges
Objekt
f"ur
Beschreibung
Nes
ted
Tabl
es94
Database Programming in SQL/ORACLE
Transactions in ORACLE
Begin of a Transaction
SET TRANSACTION READ [ONLY | WRITE];
Safepoints
For a long transaction, savepoints can be set:
SAVEPOINT <savepoint>;
End of a Transaction
• COMMIT statement: all changes become persistent,
• ROLLBACK [TO <savepoint>] undoes all changes [since<savepoint>],
• DDL statement (e.g. CREATE, DROP, RENAME, ALTER),
• User exits from ORACLE,
• process is killed.
Transactions 95
Database Programming in SQL/ORACLE
Referential Integrity – A First Look
• if a table that contains columns that are defined as foreignkeys by REFERENCES <table>(<column-list>) isgenerated, <table> must be already defined, and<column-list> must already be declared as PRIMARY KEY.
• When tuples are inserted, the corresponding referencedtuples must already be present.
• When tuples are deleted, the referential integrity must bepreserved.
• tables and views are deleted with DROP TABLE or DROPVIEW.
• it is not possible to delete a table that still containsreferenced tuples.
• tables which are targets of a REFERENCES declaration canbe deleted by DROP TABLE <table> CASCADE
CONSTRAINTS.
• nested tables do not support referential integrity.
Referential Integrity 96
Database Programming in SQL/ORACLE
PART II: This and That
Part I: Basics
• ER model and relational data model
• generation of a (relational) schema: CREATE TABLE
• queries: SELECT – FROM – WHERE
• working on the database: DELETE, UPDATE
Part II: further topics on basic SQL
• modifications of the database schema
• referential integrity
• view updates
• access control
• optimization
Part III: prodecural concepts, OO, embedding
• PL/SQL: procedures, functions, triggers
• object-orientation
• Embedded SQL, JDBC
Modifying the Database Schema 97
Database Programming in SQL/ORACLE
Modification of Schema Objects
• CREATE statement
• ALTER statement
• DROP statement
• TABLE
• VIEW
• TYPE
• INDEX
• ROLE
• PROCEDURE
• TRIGGER
...
Modifying the Database Schema 98
Database Programming in SQL/ORACLE
Modification of Table Schemata
• ALTER TABLE
• add columns and conditions,
• change conditions,
• delete, deactivate, and reactivate conditions.
ALTER TABLE <table>
ADD (<add-clause>)
MODIFY (<modify-clause>)
DROP <drop-clause>
...
DROP <drop-clause>
DISABLE <disable-clause>
...
DISABLE <disable-clause>
ENABLE <enable-clause>
...
ENABLE <enable-clause>;
Modification of Table Schemata 99
Database Programming in SQL/ORACLE
Adding Columns to Tables
ALTER TABLE <table>
ADD (<col> <datatype> [DEFAULT <value>]
[<colConstraint> ... <colConstraint>],...
<col> <datatype> [DEFAULT <value>]
[<colConstraint> ... <colConstraint>],
<add table constraints>...)
MODIFY (<modify-clause>)
DROP <drop-clause>
... ;
New columns are filled with NULL values.
Beispiel: The relation economy is extended with a columnunemployment :
ALTER TABLE Economy
ADD (Unemployment NUMBER CHECK (Unemployment > 0));
Modification of Table Schemata 100
Database Programming in SQL/ORACLE
Adding Table Conditions
ALTER TABLE <table>
ADD (<... add some columns ... >,
<tableConstraint>,...
<tableConstraint>)
MODIFY (<modify-clause>)
DROP <drop-clause>
... ;
Add an assertion that the sum of the percentages of industry,service and agriculture of the GDP is at most 100%:
ALTER TABLE Economy
ADD (Unemployment NUMBER CHECK (Unemployment > 0),
CHECK (Industry + Service + Agriculture <= 100));
• if a condition is added that does not hold in the currentdatabase state, an error message is returned.
ALTER TABLE City
ADD (CONSTRAINT citypop CHECK (Population > 100000));
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Modify Column Definitions of a Table
• column conditions can be added by ALTER TABLE ...
ADD.
ALTER TABLE <table>
ADD (<add-clause>)
MODIFY (<col> [<datatype>] [DEFAULT <value>]
[<colConstraint> ... <colConstraint>],...
<col> [<datatype>] [DEFAULT <value>]
[<colConstraint> ... <colConstraint>])
DROP <drop-clause>
... ;
• for <colConstraint>, only NULL and NOT NULL are allowedhere.
All other conditions must be added by ALTER TABLE ...
ADD (<tableConstraint>).
ALTER TABLE Country MODIFY (Capital NOT NULL);
ALTER TABLE encompasses
ADD (PRIMARY KEY (Country,Continent));
ALTER TABLE Desert
ADD (CONSTRAINT DesertArea CHECK (Area > 10));
• Error message, if a condition is added that is not satisfiedin the current database state.
Modification of Table Schemata 102
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ALTER TABLE ... DROP/DISABLE/ENABLE
• (Integrity)constraints on a table
- delete,
- deactivate for some time,
- reactivate.
ALTER TABLE <table>
ADD (<add-clause>)
MODIFY (<modify-clause>)
DROP PRIMARY KEY [CASCADE] |
UNIQUE (<column-list>) |
CONSTRAINT <constraint>
DISABLE PRIMARY KEY [CASCADE] |
UNIQUE (<column-list>) |
CONSTRAINT <constraint> | ALL TRIGGERS
ENABLE PRIMARY KEY |
UNIQUE (<column-list>) |
CONSTRAINT <constraint> | ALL TRIGGERS;
• PRIMARY KEY must not be deleted/disabled as long as thereis a REFERENCES declaration to it.
• DROP PRIMARY KEY CASCADE deletes/disablescorresponding REFERENCES declarations.
• ENABLE: if some constraints have been disabledcascadingly, they must be reactivated manually.
Modification of Table Schemata 103
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Referential Integrity
Referential integrity occur when in the transformation from theER model to the relational model, key attributes of entities areincorporated into the relationship tables (correspondencebetween primary and foreign keys):
continent Countryencompasses
name
Europe
code
R
percent
20CREATE TABLE Country
(Name VARCHAR2(32),
Code VARCHAR2(4) PRIMARY KEY,
...);
CREATE TABLE Continent
(Name VARCHAR2(10) PRIMARY KEY,
Area NUMBER(2));
CREATE TABLE encompasses
(Continent VARCHAR2(10) REFERENCES Continent(Name),
Country VARCHAR2(4) REFERENCES Country(Code),
Percentage NUMBER);
Referential Integrity 104
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Referential Integrity
Country
Name Code Capital Province
Germany D Berlin Berlin
United States USA Washington Distr. Columbia
. . . . . . . . . . . .
City
Name Country Province
Berlin D Berlin
Washington USA Distr. Columbia
. . . . . . . . .
FOREIGN KEY (<attr-list>)
REFERENCES <table’> (<attr-list’>)
• (<attr-list’>) must be a candidate key of the referencedtable.
• in ORACLE: must be declared as primary key.
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Referential Integrity
• as column condition:
<attr> [CONSTRAINT <name>]
REFERENCES <table’>(<attr’>)
CREATE TABLE City
(...
Country VARCHAR2(4)
CONSTRAINT CityRefsCountry
REFERENCES Country(Code) );
• as table condition:
[CONSTRAINT <name>]
FOREIGN KEY (<attr-list>)
REFERENCES <table’>(<attr-list’>)
CREATE TABLE Country
(...
CONSTRAINT CapitalRefsCity
FOREIGN KEY (Capital,Code,Province)
REFERENCES City(Name,Country,Province) );
Referential Integrity 106
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Referential Actions
• if the contents of a table changes, actions are carried outfor preserving referential integrity,
• if this is not possible, the changes are not executed, oreven undone.
1. INSERT into a referenced table or DELETE from a referencingtable does not cause any problems:
INSERT INTO Country
VALUES (’Lummerland,’LU’,...);
DELETE FROM is_member (’D’,’EU’);
2. INSERT or UPDATE in a referencing table must not generateforeign key values that do not exist in the referenced table:
INSERT INTO City
VALUES (’Karl-Marx-Stadt’,’DDR’,...);
If the target key exists, there is no problem:UPDATE City SET Country=’A’ WHERE Name=’Munich’;
3. DELETE und UPDATE of the referenced table: it is useful toadapt the referencing table by referential actionsautomatically:UPDATE Country SET Code=’UK’ WHERE Code=’GB’; orDELETE FROM Country WHERE Code=’I’;
Referential Integrity 107
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Referential Actions in the SQL-2 Standard
NO ACTION:
The operation is executed; after execution, it is checked,whether “dangling references” occurred. If so, theoperation is undone:DELETE FROM River;
distinguish between the reference River - River and located- River !
RESTRICT:
The operation is executed only if no “dangling references”can occur:DELETE FROM Organization WHERE ...;
error message if an organization would be deleted that stillhas some members.
CASCADE:
The operation is executed. Referencing tuples are alsodeleted or modified.UPDATE Country SET Code=’UK’ WHERE Code=’GB’;
modifies also other tables:
Country: (United Kingdom,GB,. . . ) ;
(United Kingdom,UK,. . . )Province:(Yorkshire,GB,. . . ) ; (Yorkshire,UK,. . . )City: (London,GB,Greater London,. . . ) ;
(London,UK,Greater London,. . . )
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Referential Actions in the SQL-2 Standard
SET DEFAULT:
the operation is executed and for all referenced tuples, theforeign key value is set to the specified DEFAULT values (forwhich a corresponding tuple in the referenced relation mustexist).
SET NULL:
the operation is executed and for all referenced tuples, theforeign key value is set to the NULL value (for this, NULLvalues must be allowed).
located: city is located as a river/sea/lakelocated(Bremerhaven,Nds.,D,Weser,NULL,North Sea)
DELETE * FROM River WHERE Name=’Weser’;
located(Bremerhaven,Nds.,D,NULL,NULL,North Sea)
Referential Integrity 109
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Referential Actions in the SQL-2-Standard
Referential integrity constraints and referential actions arespecified with the CREATE TABLE or ALTER TABLE command as
<columnConstraint> (for individual columns)
<col> <datatype>
CONSTRAINT <name>
REFERENCES <table’> (<attr’>)
[ ON DELETE {NO ACTION | RESTRICT | CASCADE |
SET DEFAULT | SET NULL } ]
[ ON UPDATE {NO ACTION | RESTRICT | CASCADE |
SET DEFAULT | SET NULL } ]
or <tableConstraint> (for multiple columns)
CONSTRAINT <name>
FOREIGN KEY (<attr-list>)
REFERENCES <table’> (<attr-list’>)
[ ON DELETE ...]
[ ON UPDATE ...]
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Referential Actions
Country
Name Code Capital Province
Germany D Berlin Berlin
United States USA Washington Distr. Columbia
. . . . . . . . . . . .
City
Name Country Province
Berlin D Berlin
Washington USA Distr. Columbia
. . . . . . . . .
CASCADE
NO ACTION
1. DELETE FROM City WHERE Name=’Berlin’;
2. DELETE FROM Country WHERE Name=’Germany’;
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Referential Actions in ORACLE
• ORACLE 9: only ON DELETE/UPDATE NO ACTION, ONDELETE CASCADE, and ON DELETE SET NULL areimplemented.
• of no ON ... is specified, NO ACTION is used by default.
• ON UPDATE CASCADE is missing, which is cumbersomewhen applying updates.
• This has its reasons . . .
Syntax as <columnConstraint>:
CONSTRAINT <name>
REFERENCES <table’> (<attr’>)
[ON DELETE CASCADE|ON DELETE SET NULL]
Syntax as <tableConstraint>:
CONSTRAINT <name>
FOREIGN KEY [ (<attr-list>)]
REFERENCES <table’> (<attr-list’>)
[ON DELETE CASCADE|ON DELETE SET NULL]
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Referential Actions: UPDATE without CASCADE
Beispiel: Renaming of a country:
CREATE TABLE Country
( Name VARCHAR2(32) NOT NULL UNIQUE,
Code VARCHAR2(4) PRIMARY KEY);
(’United Kingdom’,’GB’)
CREATE TABLE Province
( Name VARCHAR2(32)
Country VARCHAR2(4) CONSTRAINT ProvRefsCountry
REFERENCES Country(Code));
(’Yorkshire’,’GB’)
Now, the country code should be changed from ’GB’ to ’UK’.
• UPDATE Country SET Code=’UK’ WHERE Code=’GB’;
; “dangling reference” of the old tuple (’Yorkshire’,’GB’).
• UPDATE Province SET Code=’UK’ WHERE Code=’GB’;
; “dangling reference” of the new tuple (’Yorkshire’,’UK’).
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Referential Actions: UPDATE without CASCADE
• disable referential integrity constraint,
• apply updates,
• reactivate referential integrity constraint:
ALTER TABLE Province
DISABLE CONSTRAINT ProvRefsCountry;
UPDATE Country
SET Code=’UK’ WHERE Code=’GB’;
UPDATE Province
SET Country=’UK’ WHERE Country=’GB’;
ALTER TABLE Province
ENABLE CONSTRAINT ProvRefsCountry;
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Referential Integrity Constraints
It is also possible to define a constraint with the table definition,and immediately disable it:
CREATE TABLE <table>
( <col> <datatype> [DEFAULT <value>]
[<colConstraint> ... <colConstraint>],...
<col> <datatype> [DEFAULT <value>]
[<colConstraint> ... <colConstraint>],
[<tableConstraint>],...
[<tableConstraint>])
DISABLE ......
DISABLE ...
ENABLE ......
ENABLE ...;
Referential Integrity 115
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Referential Actions: Cyclic References
Country
Name Code Capital Province
Germany D Berlin Berlin
United States US Washington Distr.Col.
. . . . . . . . . . . .
Province
Name Country Capital
Berlin D Berlin
Distr.Col. US Washington
. . . . . . . . .
City
Name Country Province
Berlin D B
Washington USA Distr.Col.
. . . . . . . . .
Referential Integrity 116
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Referential Actions: Problems with ON UPDATE
Country
Name Code Capital Province
Germany D Berlin Berlin
United States US Washington Distr.Col.
. . . . . . . . . . . .
Province
Name Country Capital
Berlin D Berlin
Distr.Col. US Washington
. . . . . . . . .
City
Name Country Province
Berlin D B
Washington USA Distr.Col.
. . . . . . . . .
DELETE FROM Country
WHERE Code=’D’
SET NULL
CASCADE
CASCADE
Referential Integrity 117
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Referential Actions
General case:
• already a single update may be ambiguous or eveninconsistent when ON DELETE/UPDATE SET NULL/SET
DEFAULT and ON UPDATE CASCADE are allowed.
• Due to SQL triggers an update often induces several otherupdates,
• non-trivial decision which updates should be triggered,
• in case of inconsistencies, their origin must be analyzed,and maximal admissible subsets must be investigated,
• stable models, exponential complexity.
Investigations on this topic in the dbis group:
• B. Ludäscher, W. May, and G. Lausen: Referential Actionsas Logical Rules. In Proc. 16th ACM Symposium onPrinciples of Database Systems, Tucson, Arizona, 1997.
• B. Ludäscher, W. May: Referential Actions: From LogicalSemantics to Implementation. In Proc. 6th Intl. Conf. onExtending Database Technologies, Valencia, Spain, 1998.
• W. May, B. Ludäscher: Understanding the GlobalSemantics of Referential Actions using Logical Rules. InACM Transactions on Database Systems, 27(4), 2002.
Referential Integrity 118
Database Programming in SQL/ORACLE
Views
• Combination with access permissions (later)
• presentation of the actual database in a different form forsome users.
View Updates
• must be mapped onto updates of the base relation(s),
• not always possible.
• Table USER_UPDATABLE_COLUMNS in the Data Dictionary:
CREATE VIEW <name> AS ...
SELECT * FROM USER_UPDATABLE_COLUMNS
WHERE Table_Name = ’<NAME>’;
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View Updates
• derived values cannot be changed:
Example:
CREATE OR REPLACE VIEW temp AS
SELECT Name, Code, Area, Population,
Population/Area AS Density
FROM Country;
SELECT * FROM USER_UPDATABLE_COLUMNS
WHERE Table_Name = ’TEMP’;
Table_Name Column_Name UPD INS DEL
temp Name yes yes yes
temp Code yes yes yes
temp Area yes yes yes
temp Population yes yes yes
temp Density no no no
INSERT INTO temp (Name, Code, Area, Population)
VALUES (’Lummerland’,’LU’,1,4)
SELECT * FROM temp where Code = ’LU’;
• analogously for values that are computed by aggregatefunctions (COUNT, AVG, MAX, . . . )
View Updates 120
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View Updates
Example:
CREATE VIEW CityCountry (City, Country) AS
SELECT City.Name, Country.Name
FROM City, Country
WHERE City.Country = Country.Code;
SELECT * FROM USER_UPDATABLE_COLUMNS
WHERE Table_Name = ’CITYCOUNTRY’;
Table_Name Column_Name UPD INS DEL
CityCountry City yes yes yes
CityCountry Country no no no
• city names can be changed:direct mapping to City :
UPDATE CityCountry
SET City = ’Wien’
WHERE City = ’Vienna’;
SELECT * FROM City WHERE Country = ’A’;
Name Country Province . . .
Wien A Vienna . . ....
......
...
View Updates 121
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View Updates
Example:
• Country cannot be changed:
City Country
Berlin Germany
Freiburg Germany
Mapping to base table would be ambiguous:
UPDATE CityCountry UPDATE CityCountry
SET Country = ’Poland’ SET Country = ’Deutschland’
WHERE City = ’Berlin’; WHERE Country = ’Germany’;
DELETE FROM CityCountry DELETE FROM CityCountry
WHERE City = ’Berlin’; WHERE Country = ’Germany’;
View Updates 122
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View Updates
• ORACLE: admissibility decided by heuristics,
• based only on schema information,
• not on the current database state!
• key properties are important.
• Key of a base table = key of the view:obvious mapping possible and unambiguous.
• key of a base table covers a key of the view: unambiguoustranslation, several tuples of the base table can be effected.
• key of a base table does not cover any key of the view: ingeneral, no translation possible (see exercises).
View Updates 123
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View Updates
Example:
CREATE OR REPLACE VIEW temp AS
SELECT country, population
FROM Province A
WHERE population = (SELECT MAX(population)
FROM Province B
WHERE A.Country = B.Country);
SELECT * FROM temp WHERE Country = ’D’;
Country Name Population
D Nordrhein-Westfalen 17816079
UPDATE temp
SET population = 0 where Country = ’D’;
SELECT * FROM Province WHERE Name = ’D’;
Result: the population of the province with the highestpopulation in Germany is set to 0. Thus, the view changes!
SELECT * FROM temp WHERE Country = ’D’;
Country Name Population
D Bayern 11921944
View Updates 124
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View Updates
• Tuples can drop out of the view definition,
• this can be prevented by the WITH CHECK OPTION:
Beispiel
CREATE OR REPLACE VIEW UScities AS
SELECT *
FROM City
WHERE Country = ’USA’
WITH CHECK OPTION;
UPDATE UScities
SET Country = ’D’ WHERE Name = ’Miami’;
FEHLER in Zeile 1:
ORA-01402: Verletzung der WHERE clause
einer View WITH CHECK OPTION
• it is allowed to delete tuples from the view/base relation.
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Materialized Views
• Views are computed from scratch for every query.
+ always represent the current database state.
- time-consuming, inefficient if the data changes onlyseldom.
⇒ Materialized Views
• are computed at definition time, and
• are updated whenever base relations change (e.g., bytriggers).
• ⇒ problems of view maintenance.
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User Authentification
• user name
• password
• sqlplus /: authorization via UNIX account
Access Permissions inside ORACLE
• access permissions associated to the ORACLE account
• initially defined by the DBA
Schema Concept
• each user is assigned an own database schema where hisobjects are located.
• global addressing of tables by <username>.<table>
(e.g. dbis.City),
• in the own schema by <table>.
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System Privileges
• entitle for schema operations
• CREATE [ANY]
TABLE/VIEW/TYPE/INDEX/CLUSTER/TRIGGER/PROCEDURE:user is allowed to generate schema objects of these types,
• ALTER [ANY] TABLE/TYPE/TRIGGER/PROCEDURE:user is allowed to change schema objects of these types,
• DROP [ANY]
TABLE/VIEW/TYPE/INDEX/CLUSTER/TRIGGER/PROCEDURE:user is allowed to delete schema objects of these types,
• SELECT/INSERT/UPDATE/DELETE [ANY] TABLE:user is allowed to read/create/change/delete tuples fromtables.
• ANY: operation is allowed in all schemas,
• without ANY: operation is allowed only in the own schema.
In this course:
• CREATE SESSION, ALTER SESSION, CREATE TABLE,
CREATE VIEW, CREATE SYNONYM, CREATE CLUSTER.
• permissions for accessing and changing the own tables arenot mentioned explicitly (SELECT TABLE).
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System Privileges
GRANT <privilege-list>
TO <user-list> | PUBLIC [ WITH ADMIN OPTION ];
• PUBLIC: every user gets a permission
• ADMIN OPTION: the grantee is allowed to grant thispermission to other users.
Revoke permissions:
REVOKE <privilege-list> | ALL
FROM <user-list> | PUBLIC;
only if the user has granted this permission (cascading in thecase of ADMIN OPTION).
Examples:
• GRANT CREATE ANY INDEX, DROP ANY INDEX
TO opti-person WITH ADMIN OPTION;
allows opti-person to create and delete indexeseverywhere,
• GRANT DROP ANY TABLE TO destroyer;
GRANT SELECT ANY TABLE TO supervisor;
• REVOKE CREATE TABLE FROM clueless;
Informations about access permissions in the data dictionary:
SELECT * FROM SESSION_PRIVS;
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Object Privileges
allow for executing operations to existing schema objects.
• owner of a database object
• nobody else is allowed to use this object, except
• owner (or DBA) explicitly grants him some permissions:
GRANT <privilege-list> | ALL [(<column-list>)]
ON <object>
TO <user-list> | PUBLIC
[ WITH GRANT OPTION ];
• <object>: TABLE, VIEW, PROCEDURE/FUNCTION, TYPE,
• tables and views: detailed specification for INSERT,REFERENCES, and UPDATE by <column-list>,
• <privilege-list>: DELETE, INSERT, SELECT, UPDATEfor tables and views,INDEX, ALTER, and REFERENCES for tables,EXECUTE for procedures, functions, and TYPEs.
• ALL: all privileges that one has for the corresponding object.
• GRANT OPTION: the grantee can grant the permission toother users.
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Object Privileges
Revoke permissions:
REVOKE <privilege-list> | ALL
ON <object>
FROM <user-list> | PUBLIC
[CASCADE CONSTRAINTS];
• CASCADE CONSTRAINTS (bei REFERENCES): all referentialintegrity constraints, that are based on the revokedREFERENCES privilege are dropped.
• in case that a permission is obtained from several users, itis dropped with the last REVOKE.
• in case of GRANT OPTION, the revocation also cascades.
Granted and obtained permissions are stored in the DataDictionary:
SELECT * FROM USER_TAB_PRIVS;
• permissions that one has granted for the own tables,
• permissions that one has obtained for other’s tables
SELECT * FROM USER_COL_PRIVS;
SELECT * FROM USER_TAB/COL_PRIVS_MADE/RECD;
User roles are defined as prototypical patterns for maintainingpermissions (e.g., student, dba, ...).
Access Permissions 131
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Synonyms
Schema objects can be accessed under another name asoriginally stored:
CREATE [PUBLIC] SYNONYM <synonym>
FOR <schema>.<object>;
• Without PUBLIC: Synonym is defined only for its owner.
• PUBLIC creates system-wide synonyms. Only allowed ifone has the CREATE ANY SYNONYM privilege.
Example: A user often needs the relation “City” from the “dbis”schema.
• SELECT * FROM dbis.City;
• CREATE SYNONYM City
FOR dbis.City;
SELECT * FROM City;
Delete synonyms: DROP SYNONYM <synonym>;
Access Permissions 132
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Access Restriction via Views
• GRANT SELECT cannot be restricted to columns.
• instead: use a view.
GRANT SELECT [<column-list>] – nicht erlaubt
ON <table>
TO <user-list> | PUBLIC
[ WITH GRANT OPTION ];
can be replaced by
CREATE VIEW <view> AS
SELECT <column-list>
FROM <table>;
GRANT SELECT
ON <view>
TO <user-list> | PUBLIC
[ WITH GRANT OPTION ];
Access Permissions 133
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Access Restrictions via Views: Example
pol is owner of the relation Country, he wants to allow the usergeo to read and write Country without the Capital column (andthe column that gives the province where the capital is located)
View with appropriate access permissions for geo:
CREATE VIEW pubCountry AS
SELECT Name, Code, Population, Area
FROM Country;
GRANT SELECT, INSERT, DELETE, UPDATE
ON pubCountry TO geo;
• References to views are not allowed.
<pol>: GRANT REFERENCES (Code) ON Country TO geo;
<geo>: ... REFERENCES pol.Country(Code);
Access Permissions 134
Database Programming in SQL/ORACLE
Optimization of the Database
• minimize number of secondary storage accesses
• keep as much data as possible in main memory
Storage:
• efficient access (search) to secondary memory−→ access paths: indexes, hashing
• try to access data that semantically belongs together with asingle access to secondary memory−→ Clustering
Query optimization:
• keep amount of data small
• select early
• internal optimization strategies
Algorithmic optimization !
Optimization 135
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Access Paths: Indexes
Access by using indexes over columns is much more efficient.
• Trees; ORACLE: B∗-tree,
• B∗-tree: nodes contain only the information for searchingfor a value,
• high degree, height of the tree is small.
4 8 12
1 2 3 4 5 6 7 8 9 10 11 12
• searching by comparing keys: logarithmic effort.
• fast access (logarithmic) versus higher effort forreorganization (→ algorithm theory),
• multiple indexes on a table possible (over different attributesets),
• having many indexes on a table table may lead to poorperformance for insertions, modifications, and deletions,
• logically and physically independent from the data of thecorresponding table,
• no effect on the formulation of SQL statements,Optimization 136
Database Programming in SQL/ORACLE
Access Paths: Indexes
Access over indexed columns much more efficient:
• fetch index nodes from secondary memory,
• access the node that contains the tuple
CREATE TABLE zip
(City VARCHAR2(35)
Country VARCHAR2(4)
Province VARCHAR2(32)
zip NUMBER)
CREATE INDEX zipIndex ON zip (Country,zip);
SELECT *
FROM zip
WHERE zip = 79110 AND Country = ‘D’;
Optimization 137
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Hashing
Depending on the value(s) of one or more columns (hash key),a hash function is computed which indicates where thecorresponding tuples are stored.
• access in constant time,
• no order of elements.
Example:
• access to the information about a specific countryHash key: Country.Code
Hash key value
Hash function
F D NL
· · · 58317450 · · · 83536115 · · · 15568034 · · ·
547030 356910 37330
In ORACLE, hashing is implemented only for Clusters.
Optimization 138
Database Programming in SQL/ORACLE
Clusters
• collection of a group of tables which share one or morecolumns (cluster key), or
• special case: grouping of a table depending on one ormore attributes.
• with a single secondary memory access, data thatsemantically belongs together is fetched into main memory.
Advantages of clustering:
• miminize the number of secondary memory access,
• saves memory space since cluster key is stored only once.
Disadvantages:
• inefficient if cluster keys are updated frequently since thisrequires a physical reorganization,
• loss of performance when inserting into clustered tables.
Optimization 139
Database Programming in SQL/ORACLE
Clustering
Sea and geo_Sea with cluster key Sea.Name:
Cl_Sea
Mediterranean Sea Depth
5121
Province Country
Catalonia E
Valencia E
Murcia E
Andalusia E
Languedoc-R. F
Provence F...
...
Baltic Sea Depth
459
Province Country
Schleswig-H. D
Mecklenb.-Vorp. D
Szczecin PL...
...
Optimization 140
Database Programming in SQL/ORACLE
Clustering
City by (Province,Country):
Country Province
D Nordrh.-Westf. City Population . . .
Düsseldorf 572638 . . .
Solingen 165973 . . .
USA Washington City Population . . .
Seattle 524704 . . .
Tacoma 179114 . . .
......
......
...
Optimization 141
Database Programming in SQL/ORACLE
Creating a Cluster in ORACLE
Create cluster and declare cluster key:
CREATE CLUSTER <name>(<col> <datatype>-list)
[INDEX | HASHKEYS <integer> [HASH IS <funktion>]];
CREATE CLUSTER Cl_Sea (SeaName VARCHAR2(25));
Default: indexed Cluster, i.e., rows are indexed according to thecluster key.Optional: HASH, with specifying a hash function for the clusterkey values.
→֒
Optimization 142
Database Programming in SQL/ORACLE
Creating a Cluster in ORACLE
Assigning tables to a cluster by CREATE TABLE, withspecification of the cluster key.
CREATE TABLE <table>
(<col> <datatype>,...
<col> <datatype>)
CLUSTER <cluster>(<column-list>);
CREATE TABLE CSea
(Name VARCHAR2(25) PRIMARY KEY,
Depth NUMBER)
CLUSTER Cl_Sea (Name);
CREATE TABLE Cgeo_Sea
(Province VARCHAR2(32),
Country VARCHAR2(4),
Sea VARCHAR2(25))
CLUSTER Cl_Sea (Sea);
Creating the cluster key index:(must be done before the first DML command).
CREATE INDEX <name> ON CLUSTER <cluster>;
CREATE INDEX ClSeaInd ON CLUSTER Cl_Sea;
Optimization 143
Database Programming in SQL/ORACLE
Procedural Extensions: PL/SQL
• no procedural concepts in SQL (loops, if, variables)
• many tasks can only be performed awkwardly by usingintermediate tables, or even impossible:
– transitive closure
• programs represent application-specific proceduralknowledge that is not contained in the database.
Extensions
• embedding of SQL into procedural host languages(embedded SQL); e.g., C, C++, or recently Java (JDBC),
• extending SQL with procedural elements inside the SQLenvironment, PL/SQL (Procedural language extensions toSQL).
• advantages of PL/SQL: better integration of proceduralfeatures into the database: procedures, functions, andtriggers.
• required for object methods.
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Block Structure of PL/SQL
Block Header
IS
Declaration Section
BEGIN
Execution Section
EXCEPTION
Exception Section
END;
• block header: type of the object (function, procedure, oranonymous (inside another block)), and parameterdeclarations,
• declaration section: declarations of variables,
• execution section: command sequence of the block,
• exception section: reactions on errors.
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Procedures
CREATE [OR REPLACE] PROCEDURE <proc_name>
[(<parameter-list>)]
IS <pl/sql-body>;
/
• OR REPLACE: if procedure definition already exists, it isoverwritten.
• (<parameter-list>): declaration of formal parameters:
(<variable> [IN|OUT|IN OUT] <datatype>,...
<variable> [IN|OUT|IN OUT] <datatype>)
• IN, OUT, IN OUT: specify how the procedure/function usesthe parameter (read, write, both).
• default: IN.
• in case of OUT and IN OUT, the argument must always bean variable, in case of IN, also constants are allowed.
• <datatype>: all data types that are supported in PL/SQL;without length specification (VARCHAR2 instead ofVARCHAR2(20)).
• <pl/sql-body> contains the definition of the procedure inPL/SQL.
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Functions
Analogously, additionally the result type is specified:
CREATE [OR REPLACE] FUNCTION <funct_name>
[(<parameter-list>)]
RETURN <datatype>
IS <pl/sql body>;
/
• PL/SQL functions are left by
RETURN <expression>;
Each function must contain at least one RETURN statementin its <body>.
• Functions must not have side effects.
Important: after the semicolon, a slash (“/”), must follow forexecuting the declaration!!!
In case of “... created with compilation errors”:
SHOW ERRORS;
gives a more detailed error description.
Procedures and functions are deleted byDROP PROCEDURE/FUNCTION <name>.
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Procedures and Functions
• Invocation of procedures in a PL/SQL body:<procedure> (arg1,...,argn);(if a formal parameter is declared as OUT or INOUT, therespective argument must be a variable)
• Invocation of procedures in SQLPlus:execute <procedure> (arg1,...,argn);
• Usage of functions in PL/SQL:... <function> (arg1,...,argn) ...
as in other programming languages.
The system-owned table DUAL is commonly used for displayingthr return value of functions:
SELECT <function> (arg1,...,argn)
FROM DUAL;
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Example: Procedure
• Simple procedure: PL/SQL-Body contains only SQLstatements
Information about countries is distributed over several relations.
CREATE OR REPLACE PROCEDURE InsertCountry
(name VARCHAR2, code VARCHAR2, area NUMBER, pop NUMBER,
gdp NUMBER, inflation NUMBER, pop_growth NUMBER)
IS
BEGIN
INSERT INTO Country (Name,Code,Area,Population)
VALUES (name,code,area,pop);
INSERT INTO Economy (Country,GDP,Inflation)
VALUES (code,gdp,inflation);
INSERT INTO Population (Country,Population_Growth)
VALUES (code,pop_growth);
END;
/
EXECUTE InsertCountry
(’Lummerland’, ’LU’, 1, 4, 50, 0.5, 0.25);
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Example: Function
• Simple function: population density of a country
CREATE OR REPLACE FUNCTION Density (arg VARCHAR2)
RETURN number
IS
temp number;
BEGIN
SELECT Population/Area
INTO temp
FROM Country
WHERE code = arg;
RETURN temp;
END;
/
SELECT Density(’D’)
FROM dual;
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PL/SQL-Variables and Data Types.
Declaration of the PL/SQL Variables in the declaration section:
<variable> <datatype> [NOT NULL] [DEFAULT <value>];...
<variable> <datatype> [NOT NULL] [DEFAULT <value>];
Simple data types:
BOOLEAN: TRUE, FALSE, NULL,
BINARY_INTEGER, PLS_INTEGER: Signed integers,
NATURAL, INT, SMALLINT, REAL, . . . : Numerical data types.
amount NUMBER DEFAULT 0;
name VARCHAR2(30);
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anchored Type Declaration
By giving a PL/SQL variable or a table column (!) whose typeshould be used for a new variable:
<variable> <variable’>%TYPE
[NOT NULL] [DEFAULT <value>];
or
<variable> <table>.<col>%TYPE
[NOT NULL] [DEFAULT <value>];
• cityname City.Name%TYPE
use the type of the Name column of the City table as thedatatype of the newly defined variable.
• %TYPE is detected at compile time.
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Variable Assignment
• “classical way” in the program:
a := b;
• assigning a (single-column and single-row!) result of adatabase query to a PL/SQL variable:
SELECT ...
INTO <PL/SQL-Variable>
FROM ...
Example:
the_name country.name%TYPE...
SELECT name
INTO the_name
FROM country
WHERE name=’Germany’;
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PL/SQL Data Types: Records
A RECORD consists of several fields, corresponding to a tuple ofthe database:
TYPE city_type IS RECORD
(Name City.Name%TYPE,
Country VARCHAR2(4),
Province VARCHAR2(32),
Population NUMBER,
Longitude NUMBER,
Latitude NUMBER);
the_city city_type;
anchored Type Declaration for Records
Records can be declared using a table definition: %ROWTYPE:
<variable> <table-name>%ROWTYPE;
equivalent to the above example:
the_city city%ROWTYPE;
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Assignment to Records
• Aggregate assignment: two variables of the same recordtype:
<variable> := <variable’>;
• assignment of a single field:
<record.field> := <variable>|<value>;
• SELECT INTO: result of a query that yields a single tuple:
SELECT ...
INTO <record-variable>
FROM ... ;
the_country country%ROWTYPE...
SELECT *
INTO the_country
FROM country
WHERE name=’Germany’;
Comparison of Records:For comparing records, each field must be compared.
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PL/SQL Data Types: PL/SQL Tables
Array-like structure, a single column with an arbitrary datatype(including RECORD types), usually indexed by BINARY_INTEGER.
TYPE <type> IS TABLE OF <datatype>
[INDEX BY BINARY_INTEGER];
<var> <type>;
zip_table_type IS TABLE OF City.Name%TYPE
INDEX BY BINARY_INTEGER;
zip_table zip_table_type;
• Addressing: <var>(1)
zip_table(79110):= Freiburg;
zip_table(33334):= Kassel;
• sparse: only those rows are stored that actually containvalues.
Tables can also be assigned as a whole:
other_table := zip_table;
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PL/SQL Data Types: PL/SQL Tables
PL/SQL tables provide built-in functions and procedures:
<variable> := <pl/sql-table-name>.<built-in-function>;
or
<pl/sql-table-name>.<built-in-procedure>;
• COUNT (fct): number of non-empty entries.zip_table.count = 2
• EXISTS (fct): TRUE is table non-empty.
• DELETE (proc): deletes all entries of a table.
• FIRST/LAST (fct): lowest/highest used index.zip_table.first = 33334
• NEXT/PRIOR(n) (fct): yields the next higher/lower usedindex value, starting from n .zip_table.next(33334) = 79110
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SQL-Statements in PL/SQL
• DML-commands INSERT, UPDATE, DELETE, and SELECT
INTO statements.
• these SQL statements may also contain PL/SQL variables.
• commands that effect only a single tuple can assign teirresults to PL/SQL variables by using RETURNING:
UPDATE ... SET ... WHERE ...
RETURNING <expr-list>
INTO <variable-list>;
E.g., return the row-ID of the affected tuple:
DECLARE rowid ROWID;
BEGIN...
INSERT INTO Politics (Country,Independence)
VALUES (Code,SYSDATE)
RETURNING ROWID
INTO rowid;...
END;
• DDL-Statements are not supported directly by PL/SQL:DBMS_SQL-Package.
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Control Structures
• IF THEN - [ELSIF THEN] - [ELSE] - END IF,
• several kinds of loops:
• Simple LOOP: LOOP ... END LOOP;
• WHILE LOOP:WHILE <condition> LOOP ... END LOOP;
• Numeric FOR LOOP:FOR <loop_index> IN
[REVERSE] <from> .. <to>
LOOP ... END LOOP;
The variable <loop_index> is declared automatically asINTEGER.
• EXIT [WHEN <condition>]: leave LOOP.
• the well-known GOTO statement with labels:<<label_i>> ... GOTO label_j;
• NULL values always lead into the ELSE branch.
• GOTO: it is not allowed to jump into an IF, a LOOP, or a localblock; also not from one IF branch into another.
• after a label, an executable statement must follow;
• NULL Statement (is executable).
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Nested Blocks
Inside the execution section, anonymous blocks can be usedfor structuring. Here, the Declaration Section is introduced byDECLARE (there is no block header):
BEGIN
-- statements of the outer block --
DECLARE
-- declarations of the inner block
BEGIN
-- statements of the inner block
END;
-- statements of the outer block --
END;
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Cursor-Based Database Access
Row-wise access to a relation from a PL/SQL program.
Cursor declaration in the declaration section:
CURSOR <cursor-name> [(<parameter-list>)]
IS
<select-statement>;
• (<parameter-list>): parameter list.
• only IN allowed for parameter communication.
• between SELECT and FROM, PL/SQL variables and PL/SQL-Functions are allowed. PL/SQL variables can also be usedin the WHERE, GROUP, and HAVING clauses.
Example
Compute all cities which are located in the country specified bythe variable the_country:
DECLARE CURSOR cities_in
(the_country Country.Code%TYPE)
IS SELECT Name
FROM City
WHERE Country=the_country;
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Cursors
• OPEN <cursor-name>[(<argument-list>)];
creates a virtual table for the result of the given SELECT
statement and defines a “window” that is placed over oneof the tuples and can be moved forwards stepwise. OPENexecutes the query and initializes the cursor:
OPEN cities_in (’D’);
OPENName
Bonn
Kiel
Hamburg...
FETCH
FETCHFETCH
FETCH
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Cursors
• FETCH <cursor-name> INTO <record-variable>; orFETCH <cursor-name> INTO <variable-list>;
moves the cursor to the next row of the result of the queryand copies this row into the given record variable orvariable list.
The variable can e.g. be declared with the record type ofthe cursor by using <cursor-name>%ROWTYPE:
<variable> <cursor-name>%ROWTYPE;
• CLOSE <cursor-name>; closes the cursor.
Example
DECLARE CURSOR cities_in
(the_country Country.Code%TYPE)
IS SELECT Name
FROM City
WHERE Country=the_country;
city_in cities_in%ROWTYPE;
BEGIN
OPEN cities_in (’D’);
FETCH cities_in INTO city_in;
CLOSE cities_in;
END;
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Cursors
not allowed:
OPEN cities_in (’D’);
OPEN cities_in (’CH’);
FETCH cities_in INTO <variable>;
• one parameterized cursor,
• not a family of cursors!
Cursors: Attributes
• <cursor-name>%ISOPEN: Cursor open?
• <cursor-name>%FOUND: as long as the preceding FETCH
operation has been successful (i.e., the cursor has beenmoved to a valid tuple), <cursor-name>%FOUND = TRUE.
• <cursor-name>%NOTFOUND: TRUE if all rows of a cursor havebeen FETCHed.
• <cursor-name>%ROWCOUNT: number of tuples that havealready been read from the cursor.
• not allowed inside SQL expressions.
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Cursor FOR LOOP
FOR <record_index> IN <cursor-name>
LOOP ... END LOOP;
• <record_index> is automatically declared as a variable ofthe type <cursor-name>%ROWTYPE,
• <record_index> is always of a record type (includingone-column records).
• OPEN is executed automatically.
• for each execution of the loop body, FETCH is doneautomatically,
• → loop body does not contain a FETCH statement,
• at the end, CLOSE is also executed automatically,
• columns must be addressed explicitly.
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Cursor FOR LOOP
Example: for every city in a given country, a procedure“request_Info” should be invoked:
DECLARE CURSOR cities_in
(the_country country.Code%TYPE)
IS SELECT Name
FROM City
WHERE Country = the_country;
BEGIN
the_country:=’D’; % or something else
FOR the_city IN cities_in(the_country)
LOOP
request_Info(the_city.name);
END LOOP;
END;
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Cursor FOR LOOP
• SELECT statement can also be written directly into the FOR
clause.
CREATE TABLE big_cities
(name VARCHAR2(25));
BEGIN
FOR the_city IN
SELECT Name
FROM City
WHERE Country = the_country
AND Population > 1000000
LOOP
INSERT INTO big_cities
VALUES (the_city.Name);
END LOOP;
END;
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Writing on a Cursor
With WHERE CURRENT OF <cursor-name>, the most recentlyFETCHed tuple of <cursor-name> can be accessed:
UPDATE <table-name>
SET <set_clause>
WHERE CURRENT OF <cursor_name>;
DELETE FROM <table-name>
WHERE CURRENT OF <cursor_name>;
Note that the placement of the cursor over a base table tupleuniquely gives the position of the update (in contrast to ViewUpdates).
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Access Permissions
Invocation permission for functions/procedures:
• GRANT EXECUTE ON <procedure/function> TO <user>;
• procedures and functions are always executed with theaccess permissions of the owner.
• after
GRANT EXECUTE ON <procedure/function> TO <user>;
the user can execute this procedure/function, even if hehas no access permission for the tables that are used bythe procedure.
• possibility for defining access permissions that are morestrict than GRANT ... ON <table> TO ...:access is allowed only in a special context that is definedby the procedure/function.
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Nested Tables under PL/SQL
Nested_Languages
Country Languages
D German 100
CH German 65
French 18
Italian 12
Romansch 1
FL NULL
F French 100...
...
The use of nested tables in ORACLE causes some problems:“Give all countries where german is spoken, and give thepercentage of the german language in these countries”
Such a query has to search the inner table for every tuple inNested_Languages.
• SELECT THE returns only a single object,
• no correlation with the surrounding tuple.
• use a (Cursor) loop.
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Nested Tables under PL/SQL
CREATE TABLE tempCountries
(Country VARCHAR2(4),
Language VARCHAR2(20),
Percentage NUMBER);
CREATE OR REPLACE PROCEDURE Search_Countries
(the_Language IN VARCHAR2)
IS CURSOR countries IS
SELECT Code
FROM Country;
BEGIN
DELETE FROM tempCountries;
FOR the_country IN countries
LOOP
INSERT INTO tempCountries
SELECT the_country.code,Name,Percentage
FROM THE(SELECT Languages
FROM Nested_Language
WHERE Country = the_country.Code)
WHERE Name = the_Language;
END LOOP;
END;
/
EXECUTE Search_Countries(’German’);
SELECT * FROM tempCountries;PL/SQL 171
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• Up to now: functions and procedures are explicitly called bythe user.
• Triggers: invocation is caused by an event inside thedatabase.
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Intermezzo: integrity constraints
• column constraints and table constraints,
• domain constraints,
• prohobiting Null values,
• uniqueness and primary key constraints,
• CHECK-constraints,
! these are only conditions on a single row of a single table.
Assertions
• conditions that are concerned with the whole databasestate.
CREATE ASSERTION <name> CHECK (<condition>)
• not supported by ORACLE8.
⇒ other solution?
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Trigger
• special form of PL/SQL procedures,
• are invoked when a certain event takes place.
• Special case of active rules according to theEvent-Condition-Action paradigm.
• assigned to a table (often, to a certain column of this table).
• invocation is caused by detection of some event in the table(insertion, modification, or deletion of a row).
• execution also depends on a condition on the databasestate.
• action:
• before or after execution of the activating statement
• executed once per activating statement (statement trigger)or once for each effected row (Row-Trigger).
• the body of the trigger can read the old and the new valueof the tuple,
• the body of the trigger can write the new value of the tuple.
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Trigger
CREATE [OR REPLACE] TRIGGER <trigger-name>
BEFORE | AFTER
{INSERT | DELETE | UPDATE} [OF <column-list>]
[ OR {INSERT | DELETE | UPDATE} [OF <column-list>]]...
[ OR {INSERT | DELETE | UPDATE} [OF <column-list>]]
ON <table>
[REFERENCING OLD AS <name> NEW AS <name>]
[FOR EACH ROW]
[WHEN (<condition>)]
<pl/sql-block>;
• BEFORE, AFTER: trigger is invoked before/after the activatingoperation.
• OF <column> (only for UPDATE) restricts the activating eventto the specified column.
• access to the fields of the tuple before and after executingthe activating action by :OLD or :NEW. (Aliasing byREFERENCING OLD AS ... NEW AS ...).
Writing the :NEW values only with BEFORE triggers.
• FOR EACH ROW: row-Trigger, otherwise statement trigger.
• WHEN (<condition>): additional condition; OLD and NEW
are allowed in <condition>.PL/SQL 175
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Trigger: Example
If a country code is changed, this modification is propagated tothe relation Province:
CREATE OR REPLACE TRIGGER change_Code
BEFORE UPDATE OF Code ON Country
FOR EACH ROW
BEGIN
UPDATE Province
SET Country = :NEW.Code
WHERE Country = :OLD.Code;
END;
/
UPDATE Country
SET Code = ’UK’
WHERE Code = ’GB’;
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Trigger: Example
If a country is created, an entry in Politics is created with thecurrent date:
CREATE TRIGGER new_Country
AFTER INSERT ON Country
FOR EACH ROW
BEGIN
INSERT INTO Politics (Country,Independence)
VALUES (:NEW.Code,SYSDATE);
END;
/
INSERT INTO Country (Name,Code)
VALUES (’Lummerland’, ’LU’);
SELECT * FROM Politics;
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Trigger: Mutating Tables
• row-based trigger are always called immediatelybefore/after changing the row
• each invocation of the triggers sees another database stateof the table on which it is defined, and of the tables whichare changed by the trigger
• ; result depends on the order of tuples.
ORACLE: affected tables are marked as mutating during thewhole action. They cannot be read by the trigger.
Problem: a too strict criterion.
• if a trigger should access the table on which it is defined:
– only the activating tuple should be read/written by thetrigger: Use a BEFORE trigger and the :NEW and :OLD
variables
– additional tuples must be used: if possible, use astatement trigger
– otherwise, use auxiliary tables.
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INSTEAD OF Triggers
• view updates: updates must be translated to base tables.
• view updating mechanisms are restricted.
• INSTEAD OF-Trigger: modification of a view is replaced byother SQL statements.
CREATE [OR REPLACE] TRIGGER <trigger-name>
INSTEAD OF
{INSERT | DELETE | UPDATE} ON <view>
[REFERENCING OLD AS <name> NEW AS <name>]
[FOR EACH STATEMENT]
<pl/sql-block>;
• cannot be restricted to columns
• no WHEN clause
• Default: FOR EACH ROW
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View Updates and INSTEAD OF Triggers
CREATE OR REPLACE VIEW AllCountry AS
SELECT Name, Code, Population, Area,
GDP, Population/Area AS Density,
Inflation, population_growth,
infant_mortality
FROM Country, Economy, Population
WHERE Country.Code = Economy.Country
AND Country.Code = Population.Country;
INSERT INTO AllCountry
(Name, Code, Population, Area, GDP,
Inflation, population_growth, infant_mortality)
VALUES (’Lummerland’,’LU’,4,1,0.5,0,25,0);
Error message: "Uber ein Join-View kann nur eine Basistabellemodifiziert werden.
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View Updates and INSTEAD OF Triggers
CREATE OR REPLACE TRIGGER InsAllCountry
INSTEAD OF INSERT ON AllCountry
FOR EACH ROW
BEGIN
INSERT INTO
Country (Name,Code,Population,Area)
VALUES (:NEW.Name, :NEW.Code,
:NEW.Population, :NEW.Area);
INSERT INTO Economy (Country,Inflation)
VALUES (:NEW.Code, :NEW.Inflation);
INSERT INTO Population
(Country, Population_Growth,infant_mortality)
VALUES (:NEW.Code, :NEW.Population_Growth,
:NEW.infant_mortality);
END;
/
• updates Country, Economy and Population.
• trigger New_Country (AFTER INSERT ON COUNTRY) alsoupdates Politics.
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Error Handling
• Declaration Section: declaration (of names) of user-definedexceptions.
DECLARE <exception> EXCEPTION;
• Exception Section: Definition of actions that have to beexecuted in case of an exception.
WHEN <exception>
THEN <PL/SQL-Statement>;
WHEN OTHERS THEN <PL/SQL-Statement>;
• Exceptions can be raised on arbitrary places on thePL/SQL block by the RAISE statement.
IF <condition>
THEN RAISE <exception>;
Execution
• raise of an exception
• execute the corresponding action in the WHEN
• leave innermost block (use anonymous blocks)
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Triggers/Error Handling: Example
In the afternoon, it is not allowed to delete cities:
CREATE OR REPLACE TRIGGER bla
BEFORE DELETE ON City
BEGIN
IF TO_CHAR(SYSDATE,’HH24:MI’)
BETWEEN ’12:00’ AND ’18:00’
THEN RAISE_APPLICATION_ERROR
(-20101,’Unerlaubte Aktion’);
END IF;
END;
/
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Example
CREATE OR REPLACE TRIGGER bla
INSTEAD OF INSERT ON AllCountry
FOR EACH ROW
BEGIN
IF user=’may’
THEN NULL;
END IF;
...
END;
/
INSERT INTO AllCountry
(Name, Code, Population, Area, GDP, Inflation,
population_growth, infant_mortality)
VALUES (’Lummerland’,’LU’,4,1,0.5,0,25,0);
1 Zeile wurde erstellt.
SQL> select * from allcountry where Code=’LU’;
Es wurden keine Zeilen ausgewaehlt
(from A. Christiansen, M. Höding, C. Rautenstrauch andG. Saake, ORACLE 8 effizient einsetzen, Addison-Wesley,1998)PL/SQL 184
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Further PL/SQL Features
• Packages: encapsulate data and programs;
• FOR UPDATE option in cursor declarations;
• cursor variables;
• exception handlers;
• named parameter passing;
• PL-SQL built-in functions: parsing, string operations, dateoperations, numerical functions;
• built-in packages.
• definition of complex transactions,
• usage of SAVEPOINTs for transactions,
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Object-Relational Database Systems
Integration of relational concepts and object orientation:
• complex data types: extend the domain concept of SQL-2
• abstract data types (“Object types”): object identity andencapsulation of internal functionality.
• specialization: class hierarchy; subtypes as specializationof more general types.
• subtables.
• functions as parts of ADT’s or tables, or free functions.
• method calls inside of SELECT statements
Object Orientation in ORACLE 8 186
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Object Orientation
• distinction between the state and behavior of an object.
• in ORACLE 8: tables of tuples vs. object tables (whichcontain objects)
• in contrast to a tuple, an object has attributes (whichdescribe its state) and methods (for querying and changingits state).
• type defines signature of a set of instances (objects)
• already mentioned: complex attribute types, having onlyvalue attributes, no methods.
• methods: procedures and functions
• MAP/ORDER-function: order of instances of an object type
• columns in a relational table can be object-valued orreference-valued.
• Objects: value attributes and reference attributes.
• ORACLE8: no subtypes, no inheritance.
Type declaration: attributes, signatures of methods,READ/WRITE access characteristics.Type Body: implementation of the methods in PL/SQL.
Object Orientation in ORACLE 8 187
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Object Type Declarations
CREATE [OR REPLACE] TYPE <type> AS OBJECT
(<attr> <datatype>,...
<attr> REF <object-datatype>,...
MEMBER FUNCTION <func-name> [(<parameter-list>)]
RETURN <datatype>,...
MEMBER PROCEDURE <proc-name> [(<parameter-list>)],...
[ MAP MEMBER FUNCTION <func-name>
RETURN <datatype>, |
ORDER MEMBER FUNCTION <func-name>(<var> <type>)
RETURN <datatype>,]
[ <pragma-declaration-list>]
);
/
• <parameter-list> as in PL/SQL,
• similar to CREATE TABLE, but no integrity constraints (aredone later with the definition of (object) tables)
Object Orientation in ORACLE 8 188
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PRAGMA Clauses:
Read/Write Access Characteristics
<pragma-declaration-list>:
for every method, a PRAGMA clause is given:
PRAGMA RESTRICT_REFERENCES
(<method_name>, <feature-list>);
<feature-list>:
WNDS Writes no database state,
WNPS Writes no package state,
RNDS Reads no database state,
RNPS Reads no package state.
Functions: are only executed if it is explicitly asserted thatthey do not change the database state:
PRAGMA RESTRICT_REFERENCES
(<function_name>, WNPS, WNDS);
MAP/ORDER functions: no database access allowed
PRAGMA RESTRICT_REFERENCES
(<function-name>, WNDS, WNPS, RNPS, RNDS)
⇒ uses only the state of the object itself.
Object Orientation in ORACLE 8 189
Database Programming in SQL/ORACLE
Example: Geo-Coordinates
• method Distance(geo-coord-value)
• MAP method: distance from Greenwich.
CREATE OR REPLACE TYPE GeoCoord AS OBJECT
(Longitude NUMBER,
Latitude NUMBER,
MEMBER FUNCTION
Distance (other IN GeoCoord)
RETURN NUMBER,
MAP MEMBER FUNCTION
Distance_Greenwich RETURN NUMBER,
PRAGMA RESTRICT_REFERENCES
(Distance, WNPS, WNDS, RNPS, RNDS),
PRAGMA RESTRICT_REFERENCES
(Distance_Greenwich, WNPS, WNDS, RNPS, RNDS)
);
/
Object Orientation in ORACLE 8 190
Database Programming in SQL/ORACLE
Type Body
• Implementation of object methods,
• has to conform with the signature given for CREATE TYPE,
• for all declared methods, an implementation must be given.
• variable SELF for accessing the attributes of the host object.
Object Orientation in ORACLE 8 191
Database Programming in SQL/ORACLE
Type Body
CREATE [OR REPLACE] TYPE BODY <type>
AS
MEMBER FUNCTION <func-name> [(<parameter-list>)]
RETURN <datatype>
IS
[<var-decl-list>;]
BEGIN <PL/SQL-code> END;...
MEMBER PROCEDURE <proc-name> [(<parameter-list>)]
IS
[<var-decl-list>;]
BEGIN <PL/SQL-code> END;...
[MAP MEMBER FUNCTION <func-name>
RETURN <datatype> |
ORDER MEMBER FUNCTION <func-name>(<var> <type>)
RETURN <datatype>
IS
[<var-decl-list>;]
BEGIN <PL/SQL-code> END;]
END;
/
Object Orientation in ORACLE 8 192
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Object Creation
• Constructor method:
<type>(<arg_1>, ..., <arg_n>)
Method Invocation
(from a PL/SQL program)
<object>.<method-name>(<argument-list>)
using SELF, <object> can invoke its own methods.
Object Orientation in ORACLE 8 193
Database Programming in SQL/ORACLE
Example: Geo-Coordinates
CREATE OR REPLACE TYPE BODY GeoCoord
AS
MEMBER FUNCTION Distance (other IN GeoCoord)
RETURN NUMBER
IS
BEGIN
RETURN 6370 * ACOS(COS(SELF.latitude/180*3.14)
* COS(other.latitude/180*3.14)
* COS((SELF.longitude -
other.longitude)/180*3.14)
+ SIN(SELF.latitude/180*3.14)
* SIN(other.latitude/180*3.14));
END;
MAP MEMBER FUNCTION Distance_Greenwich
RETURN NUMBER
IS
BEGIN
RETURN SELF.Distance(GeoCoord(0, 51));
END;
END;
/
Object Orientation in ORACLE 8 194
Database Programming in SQL/ORACLE
Column Objects
• Attribute of a tuple (or of an object) can be object-valued,
• no OID, i.e., not referencable.
Example: Geo-Coordinates
CREATE TABLE Mountain
(Name VARCHAR2(20) CONSTRAINT MountainKey PRIMARY KEY,
Height NUMBER CONSTRAINT MountainHeight
CHECK (Height >= 0),
Coordinates GeoCoord CONSTRAINT MountainCoord
CHECK ((Coordinates.Longitude >= -180) AND
(Coordinates.Longitude <= 180) AND
(Coordinates.Latitude >= -90) AND
(Coordinates.Latitude <= 90)));
• Constraints are given as usual with the table definition:
INSERT INTO Mountain
VALUES (’Feldberg’, 1493, GeoCoord(8, 48));
SELECT Name, mt.coordinates.distance(geocoord(0, 90))
FROM Mountain mt;
• use the tuple-variable mt for disambiguating the navigationpath to coordinates.distance.
Object Orientation in ORACLE 8 195
Database Programming in SQL/ORACLE
Row Objects
• elements of Object tables,
• have a unique OID and are referencable.
• OID corresponds to the primary key and is specifiedtogether with (further) integrity constraints in the tabledefinition.
• seamless combination with referential integrity constraintsfrom object tables to existing relational tables.
CREATE TABLE <name> OF <object-datatype>
[(<constraint-list>)];
<constraint-list>:
• attribute constraints correspond to column constraints:
<attr-name> [DEFAULT <value>]
[<colConstraint> ... <colConstraint>]
• table constraints: syntax as for relational tables.
Object Orientation in ORACLE 8 196
Database Programming in SQL/ORACLE
Row Objects
Example: City_Type
CREATE OR REPLACE TYPE City_Type AS OBJECT
(Name VARCHAR2(35),
Province VARCHAR2(32),
Country VARCHAR2(4),
Population NUMBER,
Coordinates GeoCoord,
MEMBER FUNCTION Distance (other IN City_Type)
RETURN NUMBER,
PRAGMA RESTRICT_REFERENCES
(Distance, WNPS, WNDS, RNPS, RNDS));
/
CREATE OR REPLACE TYPE BODY City_Type
AS
MEMBER FUNCTION Distance (other IN City_Type)
RETURN NUMBER
IS
BEGIN
RETURN SELF.coordinates.distance(other.coordinates);
END;
END;
/
Object Orientation in ORACLE 8 197
Database Programming in SQL/ORACLE
Object Tables: Row Objects
• the (multi-column) primary key is specified as a tablecondition,
• primary key must not contain reference attributes,
• the foreign key constraint to the relational table Country isalso specified as a table condition:
CREATE TABLE City_ObjTab OF City_Type
(PRIMARY KEY (Name, Province, Country),
FOREIGN KEY (Country) REFERENCES Country(Code));
• Objects are inserted into object tables by using the objectconstructor <object-datatype>:
INSERT INTO City_ObjTab
SELECT City_Type
(Name, Province, Country, Population,
GeoCoord(Longitude, Latitude))
FROM City
WHERE Country = ’D’
AND NOT Longitude IS NULL;
Object Orientation in ORACLE 8 198
Database Programming in SQL/ORACLE
Using Objects
• select a row object as a whole,
VALUE (<var>)
in combination with aliasing
FROM <table> <var>
• e.g. for a comparison or in an ORDER BY clause.
Example
SELECT VALUE(cty)
FROM City_ObjTab cty;
VALUE (Cty)(Name, Province, Country, Population,
Coordinates(Longitude, Latitude))
City_Type(’Berlin’, ’Berlin’, ’D’, 3472009, GeoCoord(13, 52))
City_Type(’Bonn’, ’Nordrh.-Westf., ’D’, 293072, GeoCoord(8, 50))
City_Type(’Stuttgart’, ’Baden-Wuertt., ’D’, 588482, GeoCoord(9, 49))...
Object Orientation in ORACLE 8 199
Database Programming in SQL/ORACLE
Using Objects: VALUE
• check equality of objects
• object as argument of a method
SELECT cty1.Name, cty2.Name,
cty1.coordinates.Distance(cty2.coordinates)
FROM City_ObjTab cty1, City_ObjTab cty2
WHERE NOT VALUE(cty1) = VALUE(cty2);
SELECT cty1.Name, cty2.Name,
cty1.Distance(VALUE(cty2))
FROM City_ObjTab cty1, City_ObjTab cty2
WHERE NOT VALUE(cty1) = VALUE(cty2);
• assignment of an object to a PL/SQL variable by using aSELECT INTO statement:
SELECT VALUE(<var>) INTO <PL/SQL-Variable>
FROM <tabelle> <var>
WHERE ... ;
Object Orientation in ORACLE 8 200
Database Programming in SQL/ORACLE
Object References
• Additional datatype for attributes: references to objects
<ref-attr> REF <object-datatype>
• PRIMARY KEYs must not contain REF attributes.
• object type as target of a reference
• only objects that have an OID – i.e., row objects in anobject table – can be referenced.
• object type can be used in several tables
• restriction to a certain table can be specified by constraintsusing the SCOPE concept:
– as column constraint (only for relational tables):<ref-attr> REF <object-datatype>
SCOPE IS <object-table>
– as table constraint:SCOPE FOR (<ref-attr>) IS <object-table>
• generation of a reference (selection of an OID):
SELECT ..., REF(<var>), ...
FROM <object-table> <var>
WHERE ... ;
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Database Programming in SQL/ORACLE
Example: Object Type Organization
CREATE TYPE Member_Type AS OBJECT
(Country VARCHAR2(4),
Type VARCHAR2(30));
/
CREATE TYPE Member_List_Type AS
TABLE OF Member_Type;
/
CREATE OR REPLACE TYPE Organization_Type AS OBJECT
(Name VARCHAR2(80),
Abbrev VARCHAR2(12),
Members Member_List_Type,
Established DATE,
has_hq_in REF City_Type,
MEMBER FUNCTION is_member (the_country IN VARCHAR2)
-- EU.is_member(’SLO’) = ’membership applicant’
RETURN VARCHAR2,
MEMBER FUNCTION people RETURN NUMBER,
MEMBER FUNCTION number_of_members RETURN NUMBER,
MEMBER PROCEDURE add_member
(the_country IN VARCHAR2, the_type IN VARCHAR2),
PRAGMA RESTRICT_REFERENCES (is_member, WNPS, WNDS),
PRAGMA RESTRICT_REFERENCES (people, WNDS, WNPS));
PRAGMA RESTRICT_REFERENCES (number_of_members, WNDS, WNPS));
/
Object Orientation in ORACLE 8 202
Database Programming in SQL/ORACLE
Example: Object Type Organization
Table Definition:
CREATE TABLE Organization_ObjTab OF Organization_Type
(Abbrev PRIMARY KEY,
SCOPE FOR (has_hq_in) IS City_ObjTab)
NESTED TABLE Members STORE AS Members_nested;
Inserting objects via the object constructor:
INSERT INTO Organization_ObjTab VALUES
(Organization_Type(’European Community’, ’EU’,
Member_List_Type(), NULL, NULL));
Reference attribute has_hq_in:
UPDATE Organization_ObjTab
SET has_hq_in =
(SELECT REF(cty)
FROM City_ObjTab cty
WHERE Name = ’Brussels’
AND Province = ’Brabant’
AND Country = ’B’)
WHERE Abbrev = ’EU’;
Object Orientation in ORACLE 8 203
Database Programming in SQL/ORACLE
Selecting Object Attributes
• value attributes
SELECT Name, Abbrev, Members
FROM Organization_ObjTab;
Name Abbrev Members
European Community EU Member_List_Type(...)
• Reference attributes:
SELECT <ref-attr-name>
yields an OID:
SELECT Name, Abbrev, has_hq_in
FROM Organization_ObjTab;
Name Abbrev has_hq_in
European Community EU <oid>
• DEREF(<oid>) yields the corresponding object:
SELECT Abbrev, DEREF(has_hq_in)
FROM Organization_ObjTab;
Abbrev has_hq_in
EU City_Type(’Brussels’, ’Brabant’, ’B’,
951580, GeoCoord(4, 51))
Object Orientation in ORACLE 8 204
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Usage of Reference Attributes
• Attributes and methods of a referenced object areaddressed by path expressions of the form
SELECT <ref-attr-name>.<attr-name>
(“navigational access”).
• aliasing with an object variable to disambiguate the pathexpression.
SELECT Abbrev, org.has_hq_in.name
FROM Organization_ObjTab org;
Abbrev has_hq_in.Name
EU Brussels
REF and DEREF can be used instead of VALUE:
SELECT VALUE(cty) FROM City_ObjTab cty;
andSELECT DEREF(REF(cty)) FROM City_ObjTab cty;
are equivalent.
Object Orientation in ORACLE 8 205
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Cyclic References
• City_Type: country REF Country_Type
• Country_Type: capital REF City_Type
• declaration of each of the datatypes requires the definitionof some other.
• Definition of incomplete types“forward declaration”
CREATE TYPE <name>;
/
• is replaced later by a complete type declaration
Object Orientation in ORACLE 8 206
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Cyclic References: Example
CREATE OR REPLACE TYPE City_Type
/
CREATE OR REPLACE TYPE Country_Type AS OBJECT
(Name VARCHAR2(32),
Code VARCHAR2(4),
Capital REF City_Type,
Area NUMBER,
Population NUMBER);
/
CREATE OR REPLACE TYPE Province_Type AS OBJECT
(Name VARCHAR2(32),
Country REF Country_Type,
Capital REF City_Type,
Area NUMBER,
Population NUMBER);
/
CREATE OR REPLACE TYPE City_Type AS OBJECT
(Name VARCHAR2(35),
Province REF Province_Type,
Country REF Country_Type,
Population NUMBER,
Coordinates GeoCoord);
/
Object Orientation in ORACLE 8 207
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Incomplete Datatypes: Usage and Example
Incomplete datatypes can only be used for defining referencesto them, not for defining columns or nested tables:
CREATE TYPE City_type;
/
allowed:
CREATE TYPE city_list AS TABLE OF REF City_type;
/
CREATE OR REPLACE TYPE Country_Type AS OBJECT
(Name VARCHAR2(32),
Code VARCHAR2(4),
Capital REF City_Type);
/
only allowed if city_type is complete:
CREATE TYPE city_list AS TABLE OF City_type;
/
CREATE OR REPLACE TYPE Country_Type AS OBJECT
(Name VARCHAR2(32),
Code VARCHAR2(4),
Capital City_Type);
/
Object Orientation in ORACLE 8 208
Database Programming in SQL/ORACLE
Referential Integrity
• Cf. FOREIGN KEY ... REFERENCES ... ON
DELETE/UPDATE CASCADE
• modifications of objects:OID remains unchanged→ referential integrity is preserved.
• deletion of objects:dangling references possible.
Check with
WHERE <ref-attribute> IS DANGLING
Usage e.g. in an AFTER trigger:
UPDATE <table>
SET <attr> = NULL
WHERE <attr> IS DANGLING;
Object Orientation in ORACLE 8 209
Database Programming in SQL/ORACLE
Methods: Functions and Procedures
• TYPE BODY contains the implementations of the methods inPL/SQL
• PL/SQL is adapted to nested tables and someobject-oriented features.
• PL/SQL does not support navigation along pathexpressions (which is allowed in SQL).
• every MEMBER METHOD has an implicit parameter SELF thatreferences the host object itself.
• table-valued attributes can be handled inside PL/SQL likePL/SQL-tables:
Built-in methods for collections (PL/SQL-Tables) can alsobe applied to table-valued attributes:
<attr-name>.COUNT: number of tuples in the nested table
Not allowed in SQL statements that are embedded into thePL/SQL body – e.g. SELECT <attr>.COUNT.
• future extension: Java
Object Orientation in ORACLE 8 210
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CREATE OR REPLACE TYPE BODY Organization_Type IS
MEMBER FUNCTION is_member (the_country IN VARCHAR2)
RETURN VARCHAR2
IS
BEGIN
IF SELF.Members IS NULL OR SELF.Members.COUNT = 0
THEN RETURN ’no’; END IF;
FOR i in 1 .. Members.COUNT
LOOP
IF the_country = Members(i).country
THEN RETURN Members(i).type; END IF;
END LOOP;
RETURN ’no’;
END;
MEMBER FUNCTION people RETURN NUMBER IS
p NUMBER;
BEGIN
SELECT SUM(population) INTO p
FROM Country ctry
WHERE ctry.Code IN
(SELECT Country
FROM THE (SELECT Members
FROM Organization_ObjTab org
WHERE org.Abbrev = SELF.Abbrev));
RETURN p;
END;Object Orientation in ORACLE 8 211
Database Programming in SQL/ORACLE
MEMBER FUNCTION number_of_members RETURN NUMBER
IS
BEGIN
IF SELF.Members IS NULL THEN RETURN 0; END IF;
RETURN Members.COUNT;
END;
MEMBER PROCEDURE add_member
(the_country IN VARCHAR2, the_type IN VARCHAR2) IS
BEGIN
IF NOT SELF.is_member(the_country) = ’no’
THEN RETURN; END IF;
IF SELF.Members IS NULL THEN
UPDATE Organization_ObjTab
SET Members = Member_List_Type()
WHERE Abbrev = SELF.Abbrev;
END IF;
INSERT INTO
THE (SELECT Members
FROM Organization_ObjTab org
WHERE org.Abbrev = SELF.Abbrev)
VALUES (the_country, the_type);
END;
END;
/
• FROM THE(SELECT ...) cannot be replaced by FROM
SELF.Members (PL/SQL vs. SQL).Object Orientation in ORACLE 8 212
Database Programming in SQL/ORACLE
Method Calls: Functions
• MEMBER FUNCTIONS can be invoked from SQL and PL/SQLby <object>.<function>(<argument-list>).
• parameterless functions: <object>.<function>()
• from SQL: <object> is given as a path expression withalias.
SELECT Name, org.is_member(’D’)
FROM Organization_ObjTab org
WHERE NOT org.is_member(’D’) = ’no’;
• MEMBER PROCEDURES can be invoked only from PL/SQL by<object>.<procedure>(<argument-list>).
• free procedures in PL/SQL have to be used for invokingMEMBER PROCEDURES from SQL.
Object Orientation in ORACLE 8 213
Database Programming in SQL/ORACLE
Method Calls: Procedures
CREATE OR REPLACE PROCEDURE make_member
(the_org IN VARCHAR2, the_country IN VARCHAR2,
the_type IN VARCHAR2) IS
n NUMBER;
c Organization_Type;
BEGIN
SELECT COUNT(*) INTO n
FROM Organization_ObjTab
WHERE Abbrev = the_org;
IF n = 0
THEN INSERT INTO Organization_ObjTab
VALUES(Organization_Type(NULL,
the_org, Member_List_Type(), NULL, NULL));
END IF;
SELECT VALUE(org) INTO c
FROM Organization_ObjTab org
WHERE Abbrev = the_org;
IF c.is_member(the_country)=’no’ THEN
c.add_member(the_country, the_type);
END IF;
END;
/
EXECUTE make_member(’EU’, ’USA’, ’special member’);
EXECUTE make_member(’XX’, ’USA’, ’member’);
Object Orientation in ORACLE 8 214
Database Programming in SQL/ORACLE
Copying all data from the relational tables Organization andis_member to the object table Organization_ObjTab:
INSERT INTO Organization_ObjTab
(SELECT Organization_Type
(Name, Abbreviation, NULL, Established, NULL)
FROM Organization);
CREATE OR REPLACE PROCEDURE Insert_All_Members IS
BEGIN
FOR the_membership IN
(SELECT * FROM is_member)
LOOP make_member(the_membership.organization,
the_membership.country,
the_membership.type);
END LOOP;
END;
/
EXECUTE Insert_All_Members;
UPDATE Organization_ObjTab org
SET has_hq_in =
(SELECT REF(cty)
FROM City_ObjTab cty, Organization old
WHERE org.Abbrev = old.Abbreviation
AND cty.Name = old.City
AND cty.Province = old.Province
AND cty.Country = old.Country);
Object Orientation in ORACLE 8 215
Database Programming in SQL/ORACLE
Using Objects
CREATE OR REPLACE FUNCTION is_member_in
(the_org IN VARCHAR2, the_country IN VARCHAR2)
RETURN is_member.Type%TYPE IS
c is_member.Type%TYPE;
BEGIN
SELECT org.is_member(the_country) INTO c
FROM Organization_ObjTab org
WHERE Abbrev=the_org;
RETURN c;
END;
/
The system-owned table DUAL can be used for displaying theresult of free functions.
SELECT is_member_in(’EU’, ’SLO’)
FROM DUAL;
is_member_in(’EU’, ’SLO’)
applicant
It is not (at least not in ORACLE 8.0) possible to change tablecontents by using path expressions:
UPDATE Organization_ObjTab org
SET org.has_hq_in.Name = ’UNO City’ -- NOT ALLOWED
WHERE org.Abbrev = ’UN’;
Object Orientation in ORACLE 8 216
Database Programming in SQL/ORACLE
ORDER- and MAP Methods
• in contrast to most data types, object types do not have aninherent order.
• an order on objects of some type can be defined viafunctional methods.
• ORACLE 8: for each object type, a MAP FUNCTION or anORDER FUNCTION can be specified.
MAP function:
• no parameters,
• maps each object to a number.
• linear order on an object type, “absolute value”
• suitable both for comparisons <, >, and BETWEEN, and forORDER BY.
ORDER function:
• has one argument of the same object type that iscompared to the host object.
• suitable for comparisons <, >, but in general not forsorting.
• MAP and ORDER functions require PRAGMA
RESTRICT_REFERENCES (<name>, WNDS, WNPS, RNPS,
RNDS), i.e., they must not contain any database access.
Object Orientation in ORACLE 8 217
Database Programming in SQL/ORACLE
MAP Methods: Example
MAP method on GeoCoord :
CREATE OR REPLACE TYPE BODY GeoCoord
AS
...
MAP MEMBER FUNCTION Distance_Greenwich
RETURN NUMBER
IS
BEGIN
RETURN SELF.Distance(GeoCoord(0, 51));
END;
END;
/
SELECT Name, cty.coordinates.longitude,
cty.coordinates.latitude
FROM City_ObjTab cty
WHERE NOT coordinates IS NULL
ORDER BY coordinates;
Object Orientation in ORACLE 8 218
Database Programming in SQL/ORACLE
MAP Methods
Some operations are not allowed in the body of MAP methods:
• no database queries:
In Organization_Type, People cannot be used as MAP.
• no built-in methods of nested tables:
In Organization_Type, number_of_members can also notbe used as MAP method.
Object Orientation in ORACLE 8 219
Database Programming in SQL/ORACLE
ORDER Methods
• comparison between SELF an another object of the sametype that is given as a parameter.
• result: -1 (SELF < parameter), 0 (equality), or 1 (SELF >
parameter)
• in case of ORDER BY, the objects are compared pairwiseand output according to the results of the ORDER method.
• an example for this a soccer league table: a team is placedhigher than another it it has more points. In case of anequal number of point, the goal difference decides. If thisalso coincides, the number of scored goals decides (cf.exercises).
Object Orientation in ORACLE 8 220
Database Programming in SQL/ORACLE
Indexes on Attributes of Objects
Indexes can also be created over attributes of objects:
CREATE INDEX <name>
ON <object-table-name>.<attr>[.<attr>]∗;
• indexes cannot be created for complex attributes:
-- not allowed:
CREATE INDEX city_index
ON City_ObjTab(coordinates);
• indexes can be created for atomic components of complexattributes:
CREATE INDEX city_index
ON City_ObjTab(coordinates.Longitude,
coordinates.Latitude);
Access Permissions for Objects
Permission to use an object type:
GRANT EXECUTE ON <Object-datatype> TO ...
• when using an object type, its methods (including itsconstructur method) play the major role.
Object Orientation in ORACLE 8 221
Database Programming in SQL/ORACLE
Modifications of Object Types
• using object types and reference attributes induces anetwork that is similar to the one defined by keys andreferential integrity constraints.
• modifications of object types in ORACLE 8.0 are restricted:CREATE OR REPLACE TYPE and ALTER TYPE are (at least inORACLE 8.0) not allowed if the object type is usedsomewhere.
! it is not possible to add some attribute (or even only amethod!) to an object type that is used somewhere.
“In conclusion, carefully plan the object types for your databaseso that you get things right the first time. Then keep yourfingers crossed and hope that things do not change once youhave everything up and running ( ORACLE 8: Architecture)”.
Object Orientation in ORACLE 8 222
Database Programming in SQL/ORACLE
A First Conclusion
• Data management in an object-oriented schema isproblematic already for minor schema modifications.
• application-oriented (non-relational) representation bymethods and free procedures and functions.
• integration of application-specific functionality is supportedby object methods.
⇒ Data management: relational modeluser interface: object-oriented model.
Object Orientation in ORACLE 8 223
Database Programming in SQL/ORACLE
Object-Views
• powerful object views tailored to application-specificrequirements
Legacy Databases: integration of already existing databasesinto a “modern”, object-oriented model:
define object views over the relational level:“object abstractions”
Efficiency + user friendliness:relational representation is often more efficient:
• nested tables internally stored as separate tables.
• n : m-Relationships: require pairs of nested tables.
⇒ definition of a relational base schema (conceptual model)with object views (external schemata).
Modifiability: CREATE OR REPLACE TYPE and ALTER TYPE arerestricted
⇒ changes are captured by the redefinition of the object viewlevel.
Object Orientation in ORACLE 8 224
Database Programming in SQL/ORACLE
Object Views
User updates are given wrt. the external schema that is givenby object views:
• mapping of generic updates (INSERT, UPDATE, and DELETE)to the conceptual/physical schema by INSTEAD OF-Triggers,or
• generic updates are disallowed. Instead, the functionality isprovided by methods of object types that execute thechanges directly on the base tables.
Object Orientation in ORACLE 8 225
Database Programming in SQL/ORACLE
Object-Relational Views
• Tuple-views without methods:
CREATE [OR REPLACE] VIEW <name> (<column-list>) AS
<select-clause>;
• SELECT-clause: additional constructor method for objectsand nested tables.
• for creating nested tables for object views, the CAST andMULTISET constructs are used.
Example
CREATE TYPE River_List_Entry AS OBJECT
(name VARCHAR2(20),
length NUMBER);
/
CREATE TYPE River_List AS
TABLE OF River_List_Entry;
/
CREATE OR REPLACE VIEW River_V
(Name, Length, Tributary_Rivers)
AS SELECT
Name, Length,
CAST(MULTISET(SELECT Name, Length FROM River
WHERE River = A.Name) AS River_List)
FROM River A;Object Orientation in ORACLE 8 226
Database Programming in SQL/ORACLE
Object Views
• contain row objects, i.e., in this case, new objects aredefined,
• WITH OBJECT OID <attr-list> specifies how theobject-ID is computed based on the object state.
• use CAST and MULTISET.
CREATE [OR REPLACE] VIEW <name> OF <type>
WITH OBJECT OID (<attr-list>)
AS <select-statement>;
• in <select-statement> the object constructor is not usedexplicitly!
Object Orientation in ORACLE 8 227
Database Programming in SQL/ORACLE
Object Views: Country
CREATE OR REPLACE TYPE Country_Type AS OBJECT
(Name VARCHAR2(32),
Code VARCHAR2(4),
Capital REF City_Type,
Area NUMBER,
Population NUMBER);
/
CREATE OR REPLACE VIEW Country_ObjV OF Country_Type
WITH OBJECT OID (Code)
AS
SELECT Country.Name, Country.Code, REF(cty),
Area, Country.Population
FROM Country, City_ObjTab cty
WHERE cty.Name = Country.Capital
AND cty.Province = Country.Province
AND cty.Country = Country.Code;
SELECT Name, Code, c.capital.name, Area, Population
FROM Country_ObjV c;
Object Orientation in ORACLE 8 228
Database Programming in SQL/ORACLE
Object Views: what’s not (yet?) allowed
• Object View must not contain nested tables,
• and it must not contain any result of a functional method ofobjects of the base table.
Object View based on Organization_ObjTab:
CREATE OR REPLACE TYPE Organization_Ext_Type AS OBJECT
(Name VARCHAR2(80),
Abbrev VARCHAR2(12),
Members Member_List_Type,
established DATE,
has_hq_in REF City_Type,
number_of_people NUMBER);
/
CREATE OR REPLACE VIEW Organization_ObjV
OF Organization_Ext_Type
AS
SELECT Name, Abbrev, Members, established,
has_hq_in, org.people()
FROM Organization_ObjTab org;
ERROR in line 3:
ORA-00932: inconsistent datatypes
Both attributes are also not allowed alone.
Object Orientation in ORACLE 8 229
Database Programming in SQL/ORACLE
Conclusion
+ Compatibility with the basic concepts of ORACLE 7.E.g., foreign key constraints from object tables to relationaltables.
+ object views allow for an object-oriented external schema.User interaction can be mapped to the internal schema bymethods and INSTEAD OF-Triggers.
– Flexibility/Maturity:types cannot be changed/extended.(incremental!) adaptions of the schema not possible.
Object Orientation in ORACLE 8 230
Database Programming in SQL/ORACLE
New Object Relational Features inORACLE 9
• SQL type inheritance
• Object view hierarchies
• Type evolution
• User defined Aggregate Functions
• Generic and transient datatypes
• Function-based indexes
• Multi-level collections
• C++ interface to Oracle
• Java object storage
Object Orientation in ORACLE 9 231
Database Programming in SQL/ORACLE
SQL Type Inheritance
• Type hierarchy:
– supertype: parent base type
– subtype: derived type from the parent
– inheritance: connection from subtypes to supertypes ina hierarchy
• Subtype:
– adding new attributes and methods
– overriding: redefining methods
• Polymorphism: object instance of a subtype can besubstituted for an object instance of any of its subtypes
Object Orientation in ORACLE 9 232
Database Programming in SQL/ORACLE
Hierarchy example
plant
tree flower
conifer
tree: subtype of plant
supertype of conifer
Object Orientation in ORACLE 9 233
Database Programming in SQL/ORACLE
FINAL and NOT FINAL Types and Methods
• Whole type marked as FINAL:no subtypes can be derived
• Function marked as FINAL:no overriding in subtypes
Example:
CREATE TYPE coord AS OBJECT (
latitude NUMBER,
longitude NUMBER) FINAL;
/
ALTER TYPE coord NOT FINAL;
CREATE TYPE example_typ AS OBJECT (
...
MEMBER PROCEDURE display(),
FINAL MEMBER FUNCTION move(x NUMBER, y NUMBER),
...
) NOT FINAL;
/
Object Orientation in ORACLE 9 234
Database Programming in SQL/ORACLE
Creating Subtypes
Supertype is given by UNDER parameter:
CREATE TYPE coord_with_height UNDER coord (
height NUMBER
) NOT FINAL;
/
Object Orientation in ORACLE 9 235
Database Programming in SQL/ORACLE
NOT INSTANTIABLE Types and Methods
• Types declared as NOT INSTANTIABLE:
– objects of this type cannot instantiated
– no constructor
– “abstract class”
• Methods declared as NOT INSTANTIABLE:
– implementation need not to be given
– also NOT INSTANTIABLE declaration of the whole type
Examples:
CREATE TYPE generic_person_type AS OBJECT (
...
) NOT INSTANTIABLE NOT FINAL;
/
CREATE TYPE example_type AS OBJECT (
...
NOT INSTANTIABLE MEMBER FUNCTION foobar(...)
RETURN NUMBER
) NOT INSTANTIABLE NOT FINAL;
/
ALTER TYPE example_type INSTANTIABLE;
Object Orientation in ORACLE 9 236
Database Programming in SQL/ORACLE
Overloading, Overriding
• Overloading: same method name but with differentparameters (signature)
CREATE TYPE example_type AS OBJECT ( ...
MEMBER PROCEDURE print(x NUMBER),
MEMBER PROCEDURE print(x NUMBER, y NUMBER),
MEMBER PROCEDURE print(x DATE),
... ); /
• Overriding: same method name with same signature insubtypes
CREATE TYPE generic_shape AS OBJECT ( ...
MEMBER PROCEDURE draw(),
... ); /
CREATE TYPE circle_type UNDER generic_shape ( ...
MEMBER PROCEDURE draw(),
... ); /
Object Orientation in ORACLE 9 237
Database Programming in SQL/ORACLE
Attribute Substitutability
• At different places object types can be used:
– REF type attributes
– Object type attributes
– Collection type attributes
• Declared type can be substituted by any of its subtypes
• Special type forced by TREAT
Object Orientation in ORACLE 9 238
Database Programming in SQL/ORACLE
TREAT
• Function TREAT tries to modify the declared type into thespecified type,e.g. a supertype into a subtype
• Returns NULL if conversion not possible
• Supported only for SQL, not for PL/SQL
Examples:
-- types: generic_shape and subtype circle_type
-- table xy:
-- column generic_col of type generic_shape
-- column circle_col of type circle_type
UPDATE xy SET circle_col =
TREAT generic_col AS circle_type)
-- Accessing functions:
SELECT TREAT(VALUE(x) AS circle_type).area() area
FROM graphics_object_table x;
Object Orientation in ORACLE 9 239
Database Programming in SQL/ORACLE
IS OF, SYS_TYPEID
• IS OF type: object instance can be converted into specifiedtype?(same type or one of its subtypes)
Example:
-- type hierarchy:
-- plant_type ← tree_type ← conifer_type
SELECT VALUE(p)
FROM plant_table p
WHERE VALUE(p) IS OF (tree_type);
-- Result:
-- objects of type tree_type and conifer_type
• SYS_TYPEID: returns most specific type (subtype), syntax:
SYS_TYPEID(<object_type_value>)
Object Orientation in ORACLE 9 240
Database Programming in SQL/ORACLE
Summary of SQL Type Inheritance
• Type hierarchy: supertype, suptype
• FINAL, NOT FINAL types and methods
• INSTANTIABLE, NOT INSTANTIABLE types and methods
• Overloading, overriding
• Polymorphism, substitutability
• New functions: TREAT, IS OF, SYS_TYPEID
Object Orientation in ORACLE 9 241
Database Programming in SQL/ORACLE
Type Evolution
Now user-defined type may be changed:
• Add and drop attributes
• Add and drop methods
• Modify a numeric attribute (length, precision, scale)
• VARCHAR may be increased in length
• Changing FINAL and INSTANTIABLE properties
Object Orientation in ORACLE 9 242
Database Programming in SQL/ORACLE
Type Evolution: Dependencies
• Dependents: schema objects that reference a type, e.g.:
– table
– type, subtype
– PL/SQL: procedure, function, trigger
– indextype
– view, object view
• Changes: ALTER TYPE
• Propagation of type changes: CASCADE
• Compilable dependents (PL/SQL units, views, . . . ):Marked invalid and recompiled at next use
• Table: new attributes added with NULL values, . . .
Object Orientation in ORACLE 9 243
Database Programming in SQL/ORACLE
Type Evolution: Example
CREATE TYPE coord AS OBJECT (
longitude NUMBER,
latitude NUMBER,
foobar VARCHAR2(10)
name VARCHAR2(10)
);
/
ALTER TYPE coord
ADD ATTRIBUTE (height NUMBER),
DROP ATTRIBUTE foobar,
MODIFY ATTRIBUTE (name VARCHAR2(20));
Object Orientation in ORACLE 9 244
Database Programming in SQL/ORACLE
Type Evolution: Limitations
• Pass of validity checks
• All attributes from a root type cannot be removed
• Inherited attributes, methods cannot be dropped
• Indexes, referential integrity constraints of droppedattributes are removed
• Change from NOT FINAL to FINAL if no subtypes exist
• . . .
Object Orientation in ORACLE 9 245
Database Programming in SQL/ORACLE
Type Evolution: Revalidation
Fine tuning of the time for revalidation:
• ALTER TYPE:
– INVALIDATE: bypasses all checks
– CASCADE: propagation of type change to dependenttypes and tables
– CASCADE (NOT) INCLUDING TABLE DATA: user-definedcolumns
• ALTER TABLE:
– UPGRADE: conversion to latest version of each referencedtype
– UPGRADE (NOT) INCLUDING DATA: user-defined columns
Object Orientation in ORACLE 9 246
Database Programming in SQL/ORACLE
User Defined Aggregate Functions
• Set of pre-defined aggregate functions: MAX, MIN, SUM, . . .They work on scalar data.
• New aggregate functions can be written for use withcomplex data (object types, . . . ):
– feature of Extensibility Framework
– registered with the server
– usable in SQL DML statements (SELECT, . . . )
Object Orientation in ORACLE 9 247
Database Programming in SQL/ORACLE
Function-based Indexes
• Index based on the return values of a function orexpression:Return values pre-computed and stored in the index.
• Functions have to be DETERMINISTIC:
– return the same value always
– no aggregate functions inside
– nested tables, REF, . . . are not allowed
• Additional privileges:
– EXECUTE for the used functions
– QUERY REWRITE
– Some settings for Oracle to use function-based indexes
• Speed-up of query evaluation that use these functions
Object Orientation in ORACLE 9 248
Database Programming in SQL/ORACLE
Function-based Indexes: Example
CREATE TYPE emp_t AS OBJECT (
name VARCHAR2(30),
salary NUMBER,
MEMBER FUNCTION bonus RETURN NUMBER DETERMINISTIC
); /
CREATE OR REPLACE TYPE BODY emp_t IS
MEMBER FUNCTION bonus RETURN NUMBER IS
BEGIN
RETURN SELF.salary * .1;
END;
END; /
CREATE TABLE emps OF emp_t;
CREATE INDEX emps_bonus_idx ON emps x (x.bonus());
CREATE INDEX emps_upper_idx ON emps (UPPER(name));
SELECT e
FROM emps e
WHERE e.bonus() > 2000
AND UPPER(e.name) = ’ALICE’;
Object Orientation in ORACLE 9 249
Database Programming in SQL/ORACLE
Java Object Storage
• Mapping of Oracle objects and collection types into Javaclasses with automatically generated get and set
functions.
• Other direction (new in Oracle 9):SQL types that map to existing Java classesSQLJ = SQL types of Language Java
– SQL types that map to existing Java classes
– usable as object, attribute, column, row in object table
– querying and manipulating from SQL
Object Orientation in ORACLE 9 250
Database Programming in SQL/ORACLE
Java Object Storage: Example
CREATE TYPE person_t AS OBJECT
EXTERNAL NAME ’Person’ LANGUAGE JAVA
USING SQLData (
ss_no NUMBER(9) EXTERNAL NAME ’socialSecurityNo’,
name VARCHAR(30) EXTERNAL NAME ’name’,
...
MEMBER FUNCTION age () RETURN NUMBER
EXTERNAL NAME ’age () return int’,
...
STATIC create RETURN person_t
EXTERNAL NAME ’create () return Person’,
...
ORDER FUNCTION compare (in_person person_t)
RETURN NUMBER
EXTERNAL NAME ’isSame (Person) return int’
);
/
The corresponding Java class Person implements theinterface SQLData.
⇒ Next unit contains more about JDBC.
Object Orientation in ORACLE 9 251
Database Programming in SQL/ORACLE
Summary of New Features in Oracle 9
+ Introduction of inheritance
– Still missing OO features, e.g.:
– multiple inheritance
– data encapsulation (private, protected, public),but partially possible by the view concept
+ Flexibility improved: types can now be changed/extended
Object Orientation in ORACLE 9 252
Database Programming in SQL/ORACLE
Embedded SQL, JDBC
Coupling Modes between Database andProgramming Languages
• extending the database language with programmingconstructs (e.g., PL/SQL)
• extending programming languages with databaseconstructs:persistent programming languages, database programminglanguages
• embedding a database programming language into aprogramming language: “Embedded SQL”
• database access from the programming language withspecialized constructs
Embedded SQL 253
Database Programming in SQL/ORACLE
Embedded SQL
• C, Pascal, C++
Impedance Mismatch with the SQL Embedding
• type systems do not fit
• different paradigms:set-oriented vs. individual, scalar variables
Practical Solution
• Mapping of tuples/attributes to data types of the hostlanguage
• iterative processing of the result set by a cursor
Effects on the Host Language
• Structure of the host language remains unchanged
• Every SQL statement can be embedded
• SQL statements are simply prefixed by EXEC SQL
• How to communicate between application program anddatabase?
Embedded SQL 254
Database Programming in SQL/ORACLE
Development of an Embedded SQL Application
Embedded SQL/C Program
e.g. demo1.pcDB Catalog
Embedded-SQL-Precompiler
C-source code
e.g. demo1.cRuntime Library
C-Compiler/Linker
executable program
e.g. demo1Datenbank
Embedded SQL 255
Database Programming in SQL/ORACLE
Connection
Application with embedded SQL: database connection must beestablished explicitly.
EXEC SQL CONNECT :username IDENTIFIED BY :passwd;
• username and passwd host variables of the types CHAR orVARCHAR..
• strings are not allowed!
Equivalent:
EXEC SQL CONNECT :uid;
where uid is a string of the form "name/passwd".
Embedded SQL 256
Database Programming in SQL/ORACLE
Host Variables
• Communication between database and applicationprogram
• output-variables for communication of values from thedatabase to the application program
• input-variables for the communication of values from theapplication program to the database.
• assigned to each ost variable: indicator variable forhandling NULL values.
• to be declared in the Declare Section:
EXEC SQL BEGIN DECLARE SECTION;
int population; /* host variable */
short population\_ind; /* indicator variable */
EXEC SQL END DECLARE SECTION;
• in SQL-Statements, host variables and indicator variablesare prefixed with a colon (“:”)
• data types if the database and the programming languagemust be compatible
Embedded SQL 257
Database Programming in SQL/ORACLE
Indicator Variables
Handling of Null values
Indicator Variables for Output-Variables:
• -1 : the attribute value is NULL, thus, the value of the hostvariable is undefined.
• 0 : die host variable contains a valid attribute value.
• >0 : die host variable contains only a part of the attributevalue. The indicator variable gives the original length of theattribute value.
• -2 : the host variable contains only a part of the attributevalue, where the original length is not known.
Indicator Variables for Input-Variables:
• -1 : independent from the value of the host variable, thevalue NULL is inserted in the corresponding column.
• >=0 : the value of the host variable is inserted in thecorresponding column.
Embedded SQL 258
Database Programming in SQL/ORACLE
Cursors
• Analogous to PL/SQL
• required for processing a resut set that contains more thanone tuple
Cursor operations
• DECLARE <cursor-name> CURSOR FOR <sql statement>
• OPEN <cursor-name>
• FETCH <cursor-name> INTO <varlist>
• CLOSE <cursor-name>
Error Situations
• cursor has not been declared or not opened
• no (further) data has been found
• cursor has been closed, but not reopened
Current of clause analogous to PL/SQL
Embedded SQL 259
Database Programming in SQL/ORACLE
Example
int main() {
EXEC SQL BEGIN DECLARE SECTION;
char cityName[25]; /* output host var */
int cityEinw; /* output host var */
char* landID = "D"; /* input host var */
short ind1, ind2; /* indicator var */
char* uid = "/";
EXEC SQL END DECLARE SECTION;
/* Establish connection to the database */
EXEC SQL CONNECT :uid;
/* Cursor declarieren */
EXEC SQL DECLARE StadtCursor CURSOR FOR
SELECT Name, Einwohner
FROM Stadt
WHERE Code = :landID;
EXEC SQL OPEN StadtCursor; /* open cursor */
printf("Stadt Einwohner\n");
while (1)
{EXEC SQL FETCH StadtCursor INTO :cityName:ind1 ,
:cityEinw INDICATOR :ind2;
if(ind1 != -1 && ind2 != -1)
{ /* keine NULLwerte ausgeben */
printf("%s %d \n", cityName, cityEinw);
}};
EXEC SQL CLOSE StadtCursor; }Embedded SQL 260
Database Programming in SQL/ORACLE
Host Arrays
• useful if the size of the result set is known, or only apredefined portion is relevant.
• simplifies the programming, since no cursor is required.
• reduces communication overhead between client andserver.
EXEC SQL BEGIN DECLARE SECTION;
char cityName[25][20]; /* host array */
int cityPop[20]; /* host array */
EXEC SQL END DECLARE SECTION;
...
EXEC SQL SELECT Name, Population
INTO :cityName, :cityPop
FROM City
WHERE Code = ’D’;
fetches 20 tuples to the two host arrays.
Embedded SQL 261
Database Programming in SQL/ORACLE
PL/SQL
• Oracle Pro∗C/C++ precompiler supports PL/SQL blocks.
• PL/SQL block can be used in place of an SQL statement.
• PL/SQL block reduces communication overhead betweenclient and server.
• Frame for communication:
EXEC SQL EXECUTE
DECLARE
...
BEGIN
...
END;
END-EXEC;
Static vs. Dynamic SQL
SQL statements can be composed by string operations.Depending on the statements, there are several commandshow to submit these statements to the database.
Embedded SQL 262
Database Programming in SQL/ORACLE
Transactions
• Application program is regarded as a closed transaction, ifit is not divided by COMMIT- or ROLLBACK-commands
• In Oracle, after leaving a program, COMMIT is executedautomatically
• DDL statements execute COMMIT automatically before beingexecuted themselves
• the database connection is shut down byEXEC SQL COMMIT RELEASE; orEXEC SQL ROLLBACK RELEASE;
Savepoints
• Transaction can be divides by savepoints.
• Syntax : EXEC SQL SAVEPOINT <name>
• ROLLBACK to an earlier savepoint deleted all savepointsin-between.
Exception Handling Mechanism
• SQL Communications Area (SQLCA)
• WHENEVER-StatementEmbedded SQL 263
Database Programming in SQL/ORACLE
SQLCA
contains status information about the execution of the mostrecent SQL statement:
struct sqlca {
char sqlcaid[8];
long sqlcabc;
long sqlcode;
struct { unsigned short sqlerrml;
char sqlerrmc[70];
} sqlerrm;
char sqlerrp[8];
long sqlerrd[6];
char sqlwarn[8];
char sqlext[8];
};
Semantics of sqlcode:
• 0: statement has been processes without any problems.
• >0: statement has been executed, but a warning occurred.
• <0: statement has not been executed due to a seriouserror message.
Embedded SQL 264
Database Programming in SQL/ORACLE
WHENEVER-Statement
specifies actions that have to be executed automatically by theDBMS in case of an error.
EXEC SQL WHENEVER <condition> <action>;
<condition>
• SQLWARNING: the most recent statement caused a warningdifferent from “no data found” (cf. sqlwarn). Thiscorresponds to sqlcode > 0, but 6= 1403.
• SQLERROR: the most recent statement caused a seriouserror. Tis corresponds to sqlcode < 0.
• NOT FOUND: SELECT INTO or FETCH did not return any moreanswer tuple. This corresponds to sqlcode 1403.
<action>
• CONTINUE: the program continues with the subsequentstatement.
• DO flq proc_name>: invoke a procedure (error handling);DO break for exiting a loop.
• GOTO <label>: jump to the given label.
• STOP: the program is left without commit (exit()), a rollback
is executed.
Embedded SQL 265
Database Programming in SQL/ORACLE
Java and Databases
• Java: platform-independent
• if a Java Virtual Machine is available, Java programs canbe executed.
• API’s: Application Programming Interfaces; collections ofclasses and interfaces that provide a certain functionality.
JDBC: API for database access (Java DataBase Connectivity)
• interface for (remote) access to a database from Javaprograms
• application can be programmed independently from theunderlying DBMS
• translates the ODBC idea to Java
• common base is the X/Open SQL CLI (Call Level Interface)Standard
JDBC 266
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abas
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OR
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JDB
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JDB
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JDB
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Database Programming in SQL/ORACLE
JDBC Architecture
• core: driver manager
• below: driver for individual DBMSs
Types of drivers:
• Goal:
– DBMS-Client-Server-Network-Protocol with pure Javadrivers: JDBC-calls are translated to the DBMS-Networkprotocol. JDBC-client directly calls the DBMS server.
– JDBC-Net with pure Java driver: JDBC calls are translatedto the JDBC-Network protocol. At the server, they aretranslated into a certain DBMS-Protocol.
• as temporary solution:
– JDBC-ODBC-Bridge and ODBC-Driver: ODBC driver isused via a JDBC-ODBC-Bridge.
– Native API: JDBC calls are translated into calls of theclient-APIs of the corresponding database vendors.
JDBC 268
Database Programming in SQL/ORACLE
JDBC-API
• flexible:
– Application can be programmed independently from theunderlying DBMS
– de facto: portability only in the SQL-2 standard (storedprocedures, object-relational features)
• “low-level”:
– statements are submitted as strings
– in contrast to Embedded SQL, program variables inSQL commands are not allowed
Under development:
• Embedded SQL for Java
• direct mapping of tables and tuples to Java classes
JDBC 269
Database Programming in SQL/ORACLE
JDBC-Functionality
• Establishing a connection to the database(DriverManager, Connection)
• submission of SQL statements to the database (Statementand subclasses)
• processing of the result set (ResultSet)
JDBC 270
Database Programming in SQL/ORACLE
JDBC Driver Manager
DriverManager
• registration and administration of drivers
• selects a suitable driver when a connection to some DB isrequested
• establishes a connection to the requested DB
• Only one DriverManager required.
⇒ class DriverManager:
– only static methods (operating on the class)
– constructor is private (impossible to create instances)
Required drivers must be registered:
DriverManager.registerDriver(driver*)
In the SQL training for the Oracle driver:
DriverManager.registerDriver
(new oracle.jdbc.driver.OracleDriver());
creates a new instance of the Oracle driver and “gives” it to theDriver manager.
JDBC 271
Database Programming in SQL/ORACLE
Establishing a Connection
• Invocation of the DriverManager:
Connection <name> =
DriverManager.getConnection
(<jdbc-url>, <user-id>, <passwd>);
• Database is uniquely identified by the JDBC-URL
JDBC-URL:
• jdbc:<subprotocol>:<subname>
• <subprotocol> identifies the driver and access mechanism
• <subname> identifies the database
SQL training:
jdbc:oracle:<driver-name>:
@<IP-Address DB Server>:<Port>:<SID>
String url =
’jdbc:oracle:thin:@132.230.150.11:1521:o901’;
Connection conn =
DriverManager.getConnection(url,’jdbc_1’,’jdbc_1’);
returns an opened connection instance conn.
Close a connection: conn.close();
JDBC 272
Database Programming in SQL/ORACLE
Submitting SQL Statements
Statement objects:
• are created by invocation of methods of an existingconnection <connection>.
• Statement: simple SQL statements without parameters
• PreparedStatement: precompiled queries, queries withparameters
• CallableStatement: invocation of stored procedures(PL/SQL)
JDBC 273
Database Programming in SQL/ORACLE
Class “Statement”
Statement <name> = <connection>.createStatement();
Let <string> an SQL statement without semicolon.
• ResultSet <statement>.executeQuery(<string>):queries against the database. A result set is returned.
• int <statement>.executeUpdate(<string>):SQL statements that change the database. The returnvalue indicates how many tuples have been effected.
• <statement>.execute(<string>):(sequences of) statements that return more than one resultset.Result sets are then processed by invoking methods of thestatement object (see later).
A statement object can be reused for submitting SQLstatements arbitrarily often.
A statement object can be closed by its close() method.
JDBC 274
Database Programming in SQL/ORACLE
Handling of Result Sets
Class “ResultSet”:
ResultSet <name> = <statement>.executeQuery(<string>);
• virtual table that is accessible from the “Host language” – inthis case, Java.
• ResultSet object maintains a cursor which can be movedby
<result-set>.next();
to the subsequent tuple.
• <result-set>.next()
returns the value false if all tuples have been processed.
ResultSet countries =
stmt.executeQuery(“SELECT Name, Code, Population
FROM Country”);
Name code Population
Germany D 83536115
Sweden S 8900954
Canada CDN 28820671
Poland PL 38642565
Bolivia BOL 7165257
.. .. ..JDBC 275
Database Programming in SQL/ORACLE
Handling of Result Sets
• access to individual columns of the tuple where the cursoris currently placed by
<result-set>.get<type>(<attribute>)
• where <type> is a Java data type,
Java type get method
INTEGER getInt
REAL, FLOAT getFloat
BIT getBoolean
CHAR, VARCHAR getString
DATE getDate
TIME getTime
<getString> does always work.
• <attribute> can be given by the attribute name or thecolumn index.
countries.getString(“Code”);
countries.getInt(“Population”);
countries.getInt(3);
• For get<type>, the values of the result tuple (SQL-datatypes) are converted into Java types.
JDBC 276
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Han
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Res
ultS
ets
class
Hello
{
public
static
void
main
(String
args
[])
throws
SQLException
{
//
load
the
Oracledriver
DriverManager.registerDriver(new
oracle.jdbc.dnlddriver.OracleDriver());
//
connect
to
the
database
String
url
="jdbc:oracle:dnldthin:@132.230.150.161:1521:test";
Connection
conn
=DriverManager.getConnection(url,:username,:passwd);
//
submit
aquery
to
the
database
Statement
stmt
=conn.createStatement();
ResultSet
rset
=stmt.executeQuery("SELECT
Name,
Population
FROM
City");
while
(rset.next
())
{//
process
the
result
set
String
s=
rset.getString(1);
int
i=
rset.getInt("Population");
System.out.println
(s
+"
"+
i"\n");
}
}
} JDB
C27
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Database Programming in SQL/ORACLE
Handling of Result Sets
JDBC Data Types
• JDBC stands in-between Java (object types) and SQL(several types).
• java.sql.types defines generic SQL types which areused by JDBC:
Java type JDBC-SQL type
String CHAR, VARCHAR
java.math.BigDecimal NUMBER, NUMERIC, DECIMAL
boolean BIT
byte TINYINT
short SMALLINT
int INTEGER
long BIGINT
float REAL
double FLOAT, DOUBLE
java.sql.Date DATE (day, month, year)
java.sql.Time TIME (hour, minute, second)
These are also used for describing metadata.
JDBC 278
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set:
ResultSetMetaData
<name
>=
<result-set
>.getMetaData();
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JDB
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Database Programming in SQL/ORACLE
Handling of Result Sets
• no NULL values in Java:
<resultSet>.wasNULL()
tests whether the most recently read column value wasNULL.
Example: output the current row of the result set
ResultSetMetaData rsetmetadata = rset.getMetaData();
int numCols = rsetmetadata.getColumnCount();
for(i=1; i<=numCols; i++) {
String returnValue = rset.getString(i);
if (rset.wasNull())
System.out.println ("null");
else
System.out.println (returnValue);
}
• The method close() closes a ResultSet object explicitly.
JDBC 280
Database Programming in SQL/ORACLE
Prepared Statements
PreparedStatement <name> =
<connection>.prepareStatement(<string>);
• SQL statement <string> is precompiled.
• thus, the statement is contained in the state of the object
• more efficient than Statement if some statement has to beexecuted several times.
• depending on <string>, only one of the (parameterless!)methods
– <prepared-statement>.executeQuery(),
– <prepared-statement>.executeUpdate() or
– <prepared-statement>.execute()
is applicable.
JDBC 281
Database Programming in SQL/ORACLE
Prepared Statements: Parameters
• Input parameters are represented by “?”
PreparedStatement pstmt =
conn.prepareStatement("SELECT Population
FROM Country
WHERE Code = ?");
• “?”-parameters are assigned to values by
<prepared-statement>.set<type>(<pos>,<value>);
before a PreparedStatement is submitted.
• <type>: Java data type,
• <pos>: position of the parameter to be set,
• <value>: value.
pstmt.setString(1,"D");
ResultSet rset = pstmt.ExecuteQuery();
...
pstmt.setString(1,"CH");
ResultSet rset = pstmt.ExecuteQuery();
...
• Null values are set by
setNULL(<pos>,<type>);
where <type> is the JDBC type of this column:
pstmt.setNULL(1,Types.String);
JDBC 282
Database Programming in SQL/ORACLE
Callable Statements: Invoke Stored Procedures
• Stored procedures and functions are created by
<statement>.executeUpdate(<string>);
(<string> is of the form CREATE PROCEDURE ...)
s = ’CREATE PROCEDURE bla() IS BEGIN ... END’;
stmt.executeUpdate(s);
• the procedure invocation is then created as aCallableStatement object:
• invocation syntax of procedures differs amongst the DBMSproducts
⇒ JDBC uses a generic syntax via an escape-sequence(which is translated by the driver)
CallableStatement <name> =
<connection>.prepareCall("{call <procedure>}");
cstmt = conn.prepareCall("{call bla()}");
JDBC 283
Database Programming in SQL/ORACLE
Callable Statements with Parameters
s = ’CREATE FUNCTION
distance(city1 IN Name, city2 IN Name)
RETURN NUMBER IS BEGIN ... END’;
stmt.executeUpdate(s);
• Parameters:
CallableStatement <name> =
<connection>.prepareCall("{call <procedure>(?,...,?)}");
• Return value of functions:
CallableStatement <name> =
<connection>.prepareCall
("{? = call <procedure>(?,...,?)}");
cstmt = conn.prepareCall("{? = call distance(?,?)}");
• for OUT-parameters and the return value, the JDBC datatype of the parameters must first be registered by
<callable-statement>.registerOutParameter
(<pos>,java.sql.Types.<type>);
cstmt.registerOutParameter(1,java.sql.types.number);
JDBC 284
Database Programming in SQL/ORACLE
Callable Statements with Parameters
• Preparations (see above)
cstmt = conn.prepareCall("{? = call distance(?,?)}");
cstmt.registerOutParameter(1,java.sql.types.number);
• IN parameters are set by set<type>:
cstmt.setString(2,’Freiburg’);
cstmt.setString(3,’Berlin’);
• invocation by
ResultSet <name> =
<callable-statement>.executeQuery();
or
<callable-statement>.executeUpdate();
or
<callable-statement>.execute();
in our example: cstmt.execute();
• OUT-parameters are read by get<type>:
int distance = cstmt.getInt(1);
JDBC 285
Database Programming in SQL/ORACLE
Sequential Execution
• SQL-Statements that return a sequence of result sets:
• <statement>.execute(<string>),<prepared-statement>.execute(),<callable-statement>.execute()
• Often <string> is generated dynamically
• getResultSet() or getUpdateCount():gets the next return value or update count.
• getMoreResults() and then againgetResultSet() or getUpdateCount():proceed to the next result.
JDBC 286
Database Programming in SQL/ORACLE
Sequential Execution
• getResultSet(): if the next result is a result set, this isreturned. If no next result is available, or the next result isan update count, null is returned.
• getUpdateCount(): if the next result is an update count,this (n ≥ 0) is returned. If no next result is available, or thenext result is a result set, -1 is returned.
• getMoreResults(): true, if the next result is a result set,false, if it is an update count or there are no more results.
• test if all results are processed:
((<stmt>.getResultSet() == null) &&
(<stmt>.getUpdateCount() == -1))
or
((<stmt>.getMoreResults() == false) &&
(<stmt>.getUpdateCount() == -1))
JDBC 287
Database Programming in SQL/ORACLE
Handling a Sequence of Results
stmt.execute(queryStringWithUnknownResults);
while (true) {
int rowCount = stmt.getUpdateCount();
if (rowCount > 0) {
System.out.println("Rows changed = " + count);
stmt.getMoreResults();
continue;
}
if (rowCount == 0) {
System.out.println("No rows changed");
stmt.getMoreResults();
continue;
}
ResultSet rs = stmt.getResultSet();
if (rs != null) {
..... // process metadata
while (rs.next())
{ ....} // process result set
stmt.getMoreResults();
continue;
}
break;
}
JDBC 288
Database Programming in SQL/ORACLE
Further SQL/Oracle Tools
• Dynamic SQL: SQL statements are generated in in PL/SQLat runtime as strings, and are then submitted to thedatabase.
• ORACLE8i: built-in Java Virtual Machine, access to the filesystem,i= internet: XML-interface, Web-Application-Server etc.
• ORACLE-Web Server/Internet Application Server (9i):HTML pages can be generated depending on the databasecontents.
• by the most recent packages and extensions (IAS, InternetFile System Server) the difference between the databaseand the operating system diminishes.
JDBC 289
Database Programming in SQL/ORACLE
ORACLE8?
+ complex data types
+ Objects: object methods, object references, pathexpressions⇒ user-friendly interface possible(vgl. add_member, is_member )
– Nested Tables:
– Storage: as separate tables (STORE AS ...)
– DML: cumbersome SELECT FROM THE, TABLE ..., CASTMULTISET
– usage: query must only consider a single nested table⇒ cursor requires
– no advantages ??
– modifications of object types not supported⇒ object types not suitable for storage.
• “I think this is the power of the system. Object Views.”
Summary 290
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Database Programming in SQL/ORACLE
• Modifications of the relational storage: easy.Implementations of the object types can be adaptedwithout changing the user interface (external schema).
• Modifications of the object types: independent of thestorage (Views). Possible to delete object types completelyand rebuild new ones without losing data.
• Adding functionality: redefine or add suitable object types.
Summary 292